Out-of-band communication channel for subcarrier-based optical communication systems

ABSTRACT

An example system includes a hub transceiver and a plurality of edge transceivers. The hub transceiver is operable to transmit, over a first communications channel, a first message to each of the edge transceivers concurrently, including an indication of available network resources on an optical communications network. Each of the edge transceiver is operable to transmit, transmit, over a second communications channel, a respective second message to the hub transceiver including an indication of a respective subset of the available network resources selected by the edge transceiver for use in communicating over the optical communications network. Further, the edge transceiver is operable to receive, from the hub transceiver, a third message acknowledging receipt of a selection and a fourth message confirming an assignment of the selected subset of the available network resources to the edge transceiver.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.16/893,357, which claims the benefit of U.S. patent application Ser. No.16/578,078, filed Sep. 20, 2019; U.S. Provisional Patent Application No.62/857,128, filed Jun. 4, 2019; U.S. Provisional Patent Application No.62/937,060, filed Nov. 18, 2019, which are incorporated herein byreference in their entirety.

TECHNICAL FIELD

This disclosure relates to transmitting and receiving data using opticalcommunications networks.

BACKGROUND

Optical communication systems typically include a first node thatoutputs optical carriers to one or more second nodes. The first andsecond nodes are connected to each other by one or more segments ofoptical fiber. The nodes in an optical communication system may include,for example, an internet protocol (IP) router, as well as a transceivermodule that often plugs into the router and connects to the opticalcommunication system fibers. In many circumstances, the transceivermodules and other node equipment, such as the router, are provided bythe same vendor. As such, monitoring, status, and control informationassociated with the transceiver modules is communicated to a user'scentral software through the router or other node equipment. An opticalservice channel (OSC) or Ethernet connection, for example, may becoupled to an external port on the node equipment to provide themonitoring, status, and control information to the central software.However, the central software typically cannot access or manage thetransceiver modules independently of the node equipment. Moreover,transceiver modules typically do not communicate directly with otherequipment in the communication system, such as equipment coupled alongthe optical fibers (“line system components”) in the system as well asother transceivers. That is, transceivers are typically not separatelyaddressable managed entities from the node equipment and lack a directdata path for communicating control information to/from the transceiver.Since such data paths traditionally are made through the node equipment,transceivers purchased from a vendor other than the node equipmentvendor may be limited to a reduced set of capability that is compatiblewith the node equipment. Accordingly, such transceivers may not beadequately monitored or controlled to enable the full set of transceivercapabilities offered by devices from another vendor.

Without a capability of communicating control information directly withthe transceivers, customers may be precluded from enabling and controlof the full set of capabilities offered by devices from vendors otherthan the vendor that also supply the node equipment. Therefore, suchcustomers may not realize cost savings that would otherwise be achievedby purchasing node equipment and transceivers from different vendors.

SUMMARY

In an aspect, a system includes a hub transceiver configured to becommunicatively coupled to a first network node and to an opticalcommunications network, and to one edge transceiver or a plurality ofedge transceivers. Each of the edge transceivers is configured to becommunicatively coupled to a respective second network node and to theoptical communications network. The hub transceiver is operable totransmit, over a first communications channel of the opticalcommunications network, a first message to each of the edge transceiversconcurrently, where the first message includes an indication ofavailable network resources on the optical communications network. Eachof the edge transceivers is operable to transmit, over a secondcommunications channel of the optical communications network, arespective second message to the hub transceiver, where the secondmessage includes an indication of a respective subset of the availablenetwork resources selected by the edge transceiver for use incommunicating over the optical communications network; receive, from thehub transceiver, a third message acknowledging receipt of a selection bythe edge transceiver; receiving, from the hub transceiver, a fourthmessage confirming an assignment of the selected subset of the availablenetwork resources to the edge transceiver for use in communicating overthe optical communications network; and transmit, using the selectedsubset of the available network resources, data from the second networknode that is communicatively coupled to the edge transceiver to thefirst network node via the hub transceiver.

In another aspect, an apparatus includes an edge transceiver configuredto be communicatively coupled to a first network node and to an opticalcommunications network. The edge transceiver is operable to receive,over a first communications channel of the optical communicationsnetwork, a first message from a hub transceiver, where the first messageincludes an indication of available network resources on the opticalcommunications network; transmit, over a second communications channelof the optical communications network, a second message to the hubtransceiver, where the second message includes an indication of a subsetof the available network resources selected by the edge transceiver foruse in communicating over the optical communications network; receive,from the hub transceiver, a third message acknowledging receipt of aselection by the edge transceiver; receive, from the hub transceiver, afourth message confirming an assignment of the selected subset of theavailable network resources to the edge transceiver for use incommunicating over the optical communications network; and transmit,using the selected subset of the available network resources, data fromthe first network node to a second network node via the hub transceiver.

In another aspect, a method includes receiving, by an edge transceivercommunicatively coupled to a first network node and to an opticalcommunications network, a first message from a hub transceiver over afirst communications channel of the optical communications network,where the first message includes an indication of available networkresources on the optical communications network; transmitting, by theedge transceiver over a second communications channel of the opticalcommunications network, a second message to the hub transceiver, wherethe second message includes an indication of a subset of the availablenetwork resources selected by the edge transceiver for use incommunicating over the optical communications network; receiving, by theedge transceiver from the hub transceiver, a third message acknowledgingreceipt of a selection by the edge transceiver; receiving, by the edgetransceiver from the hub transceiver, a fourth message confirming anassignment of the selected subset of the available network resources tothe edge transceiver for use in communicating over the opticalcommunications network; and transmitting, by the edge transceiver usingthe selected subset of the available network resources, data from thefirst network node to a second network node via the hub transceiver.

In another aspect, an apparatus includes a hub transceiver configured tobe communicatively coupled to a first network node and to an opticalcommunications network. The hub transceiver is operable to transmit,over a first communications channel of the optical communicationsnetwork, a first message to each of a plurality of edge transceiversconcurrently, where the first message includes an indication ofavailable network resources on the optical communications network, andwhere each of the edge transceivers is configured to be communicativelycoupled to a respective second network node and to the opticalcommunications network; receive, from a first edge transceiver of theplurality of edge transceivers, a second message over a secondcommunications channel of the optical communications network, where thesecond message comprises an indication of a subset of the availablenetwork resources selected by the first edge transceiver for use incommunicating over the optical communications network; transmit, to thefirst edge transceiver, a third message acknowledging receipt of aselection by the first edge transceiver; assign the selected subset ofthe available network resources to the first edge transceiver for use incommunicating over the optical communications network, and transmit afourth message confirming an assignment of the selected subset of theavailable network resources to the first edge transceiver.

In another aspect, a system includes a management optical gateway (alsoreferred to as an optical gateway) configured to be communicativelycoupled to an optical communications network; a plurality of hubtransceivers, where each hub transceiver is configured to becommunicatively coupled to a respective first network node of theoptical communications network and to the optical gateway; and aplurality of edge transceivers, where each of the edge transceivers isconfigured to be communicatively coupled to a respective second networknode of the optical communications network and to the optical gateway.The optical gateway is operable to receive a plurality of signals fromthe optical communications network at a plurality of ports of theoptical gateway, where each port of the optical gateway includes one ormore respective photodiodes. Further, the optical gateway is operable totransmit a plurality of signals from the optical communications networkat a plurality of ports of the optical gateway, where a VOA (VariableOptical Attenuator) may be operable to adjust or vary the attenuation ofthe signals of the optical communications network based on a controlsignal supplied thereto. Further, the optical gateway is operable todetermine, for each port, a respective link of the opticalcommunications network communicatively coupling the port with at leastone hub transceiver of the plurality of hub transceivers or with atleast one edge transceiver of the plurality of edge transceivers, and anidentity of the at least one hub transceiver or the at least one edgetransceiver.

In another aspect, an apparatus includes an optical gateway configuredto be communicatively coupled to an optical communications network, to aplurality of hub transceivers, and to a plurality of edge transceivers.The optical gateway is operable to receive a plurality of signals fromthe optical communications network at a plurality of ports of theoptical gateway, where each port of the optical gateway comprises one ormore respective photodiodes. The optical gateway is also operable todetermine, for each port, a respective link of the opticalcommunications network communicatively coupling the port with at leastone hub transceiver communicatively coupled to the opticalcommunications network or with at least one edge transceivercommunicatively coupled to the optical communications network, and anidentity of the at least one hub transceiver or the at least one edgetransceiver.

In another aspect, a method includes receiving, by an optical gatewaycommunicatively coupled to an optical communications network, aplurality of signals from the optical communications network at aplurality of ports of the optical gateway, where each port of theoptical gateway comprises one or more respective photodiodes; anddetermining, by an optical gateway for each port, a respective link ofthe optical communications network communicatively coupling the portwith at least one hub transceiver communicatively coupled to the opticalcommunications network or with at least one edge transceivercommunicatively coupled to the optical communications network, and anidentity of the at least one hub transceiver or the at least one edgetransceiver.

In another aspect, a system includes a plurality of hub transceivers,where each hub transceiver is configured to be communicatively coupledto a respective first network node of the optical communicationsnetwork; and a plurality of edge transceivers, where each of the edgetransceivers is configured to be communicatively coupled to a respectivesecond network node of the optical communications network. A first hubtransceiver of the plurality of hub transceivers is operable todetermine that the first hub transceiver is configured to assign a firstsubset of network resources of the optical communications network to afirst subset of the edge transceivers for communication over the opticalcommunications network; determine that a second hub transceiver isconfigured to assign a second subset of network resources of the opticalcommunications network to a second subset of the edge transceivers forcommunication over the optical communications network; determine thatthe first subset of network resources overlaps the second subset ofnetwork resources; and responsive to determining that the first subsetof network resources overlaps the second subset of network resources,transmit a notification of the overlap to a control module of theoptical communications network.

In another aspect, an apparatus includes a first hub transceiverconfigured to be communicatively coupled to an optical communicationsnetwork, to a second hub transceiver, and to a plurality of edgetransceivers. The first hub transceiver is operable to determine thatthe first hub transceiver is configured to assign a first subset ofnetwork resources of the optical communications network to a firstsubset of the edge transceivers for communication over the opticalcommunications network; determine that a second hub transceiver isconfigured to assign a second subset of network resources of the opticalcommunications network to a second subset of the edge transceivers forcommunication over the optical communications network; determine thatthe first subset of network resources overlaps the second subset ofnetwork resources; responsive to determining that the first subset ofnetwork resources overlaps the second subset of network resources,transmit a notification of the overlap to a control module of theoptical communications network.

In another aspect, an apparatus includes an optical gateway configuredto be communicatively coupled to a plurality of hub transceivers. Theoptical gateway is operable to determine that a first hub transceiver ofthe plurality of hub transceivers is transmitting data to the opticalgateway according to a first frequency range; determine that a secondhub transceiver of the plurality of hub transceivers is transmittingdata to the optical gateway according to a first frequency rangetransmitting data to the optical gateway according to a second frequencyrange; determine that the first frequency range overlaps the secondfrequency range; and responsive to determining that the first frequencyrange overlaps the second frequency range, transmit a command to thesecond hub transceiver to transmit data to the optical gateway accordingto a third frequency range that does not overlap the first frequencyrange.

In another aspect, a method includes determining, by a first hubtransceiver communicatively coupled to an optical communicationsnetwork, that the first hub transceiver is configured to assign a firstsubset of network resources of the optical communications network to afirst subset of the edge transceivers for communication over the opticalcommunications network; determining, by the first hub transceiver, thata second hub transceiver is configured to assign a second subset ofnetwork resources of the optical communications network to a secondsubset of the edge transceivers for communication over the opticalcommunications network; determining, by the first hub transceiver, thatthe first subset of network resources overlaps the second subset ofnetwork resources; and responsive to determining that the first subsetof network resources overlaps the second subset of network resources,transmitting, by the first hub transceiver, a notification of theoverlap to a control module of the optical communications network.

In another aspect, a system includes a hub transceiver configured to becommunicatively coupled to a first network node and to an opticalcommunications network; a plurality of edge transceivers, where each ofthe edge transceivers is configured to be communicatively coupled to arespective second network node and to the optical communicationsnetwork; and a control module communicatively coupled to one or more ofthe hub transceiver or the plurality of edge transceivers. The controlmodule is operable to receive, from one or more of the edge transceiversor the hub transceiver, telemetry data regarding at least one of atransmission or a receipt of data over the optical communicationsnetwork; determine, based on the telemetry data, performancecharacteristics regarding the optical communications network; andtransmit, based on the performance characteristics, a command to one ormore of the edge transceivers or the hub transceiver to modify anoperation with respect to the optical communications network.

In another aspect, an apparatus includes a control modulecommunicatively coupled to one or more edge transceivers or to a hubtransceiver of an optical communications network. The control modulecomprises circuitry operable to receive, from one or more of the edgetransceivers or the hub transceiver, telemetry data regarding at leastone of a transmission or a receipt of data over the opticalcommunications network; determine, based on the telemetry data,performance characteristics regarding the optical communicationsnetwork; and transmit, based on the performance characteristics, acommand to one or more of the edge transceivers or the hub transceiverto modify an operation with respect to the optical communicationsnetwork.

In another aspect, a method includes receiving, by a control modulecommunicatively coupled to an optical communications network, from oneor more edge transceivers or hub transceiver of the opticalcommunications network, telemetry data regarding at least one of atransmission or a receipt of data over the optical communicationsnetwork; determining, by the control module based on the telemetry data,performance characteristics regarding the optical communicationsnetwork; and transmitting, by the control module based on theperformance characteristics, a command to one or more of the edgetransceivers or the hub transceiver to modify an operation with respectto the optical communications network.

In another aspect, a system includes a hub transceiver configured to becommunicatively coupled to a first network node and to an opticalcommunications network; and a plurality of edge transceivers, where eachof the edge transceivers is configured to be communicatively coupled toa respective second network node and to the optical communicationsnetwork. The hub transceiver is operable to:=determine a plurality ofoptical subcarriers available for assignment by the hub transceiver tothe plurality of the edge transceivers for use in communicating over theoptical communications network; assign, to each of the edgetransceivers, a respective subset of the optical subcarriers use incommunicating over the optical communications network, where each of thesubsets of the optical subcarriers includes a respective data opticalsubcarrier for transmitting data over the optical communicationsnetwork, and where at least one of the subsets of the opticalsubcarriers includes one or more respective idle optical subcarriers;and transmit, to each of the edge transceivers, an indication of therespective subset of the optical subcarriers assigned to the edgetransceiver. Each of the edge transceivers is operable to receive, fromthe hub transceiver, the indication of the respective subset of theoptical subcarriers assigned to the edge transceiver; and transmit dataover the optical communications network using the respective subset ofthe optical subcarriers assigned to the edge transceiver.

In another aspect, an apparatus includes a hub transceiver configured tobe communicatively coupled to a first network node and to an opticalcommunications network. The hub transceiver is operable to determine aplurality of optical subcarriers available for assignment by the hubtransceiver to a plurality of edge transceivers for use in communicatingover the optical communications network; assign, to each of the edgetransceivers, a respective subset of the optical sub carriers for use incommunicating over the optical communications network, where each of thesubsets of the optical subcarriers includes a respective data opticalsubcarrier for transmitting data over the optical communicationsnetwork, and where at least one of the subsets of the opticalsubcarriers includes one or more respective idle optical subcarriers;and transmit, to each of the edge transceivers, an indication of therespective subset of the optical subcarriers assigned to the edgetransceiver.

In another aspect, a method includes determining, by a hub transceivercommunicatively coupled to a first network node and to an opticalcommunications network, a plurality of optical subcarriers available forassignment by the hub transceiver to a plurality of edge transceiversfor use in communicating over the optical communications network;assigning, by the hub transceiver to each of the edge transceivers, arespective subset of the optical subcarriers for use in communicatingover the optical communications network, where each of the subsets ofthe optical subcarriers includes a respective data optical subcarrierfor transmitting data over the optical communications network, and whereat least one of the subsets of the optical subcarriers includes one ormore respective idle optical subcarriers; and transmitting, from the hubtransceiver to each of the edge transceivers, an indication of therespective subset of the optical subcarriers assigned to the edgetransceiver.

In another aspect, a system includes a hub transceiver configured to becommunicatively coupled to a first network node and to an opticalcommunications network; and a plurality of edge transceivers, where eachof the edge transceivers is configured to be communicatively coupled toa respective second network node and to the optical communicationsnetwork. Each of the edge transceivers has one of: a first type ofconfiguration for communicating with the optical communications networkaccording to a first bandwidth, where the first type of configuration isassociated with a first optical subcarrier assignment protocol; a secondtype of configuration for communicating with the optical communicationsnetwork according to a second bandwidth, where the second type ofconfiguration is associated with a second optical subcarrier assignmentprotocol; or a third type of configuration for communicating with theoptical communications network according to a third bandwidth, where thethird type of configuration is associated with a third opticalsubcarrier assignment protocol. The hub transceiver is operable todetermine a plurality of optical subcarriers available for assignment bythe hub transceiver to the plurality of the edge transceivers for use incommunicating over the optical communications network; assign, to eachof the edge transceivers, a respective subset of the optical subcarriersfor use in communicating over the optical communications network.Assigning the respective subset of the optical subcarriers includes, foreach particular one of the edge transceivers determining that theparticular edge transceiver has the first type of configuration, thesecond type of configuration, or the third type of configuration; and inresponse to determining that the edge transceiver has the first type ofconfiguration, the second type of configuration, or the third type ofconfiguration, assigning the respective subset of the opticalsubcarriers to the particular edge transceiver according to a particularone of the optical subcarrier assignment protocols associated with thedetermined type of configuration. The hub transceiver is also operableto transmit, to each respective one of the edge transceivers, anindication of the respective subset of the optical subcarriers assignedto the particular edge transceiver. Each particular one of the edgetransceivers is operable to receive, from the hub transceiver, theindication of the respective subset of the optical subcarriers assignedto the particular edge transceiver; and transmit data over the opticalcommunications network using the respective subset of the opticalsubcarriers assigned to the particular edge transceiver.

In another aspect, an apparatus includes a hub transceiver configured tobe communicatively coupled to a first network node and to an opticalcommunications network. The hub transceiver is operable to determine aplurality of optical subcarriers available for assignment by the hubtransceiver to a plurality of the edge transceivers for use incommunicating over the optical communications network, where each of theedge transceivers is configured to be communicatively coupled to arespective second network node and to the optical communicationsnetwork. Each of the edge transceivers has one of: a first type ofconfiguration for communicating with the optical communications networkaccording to a first bandwidth, where the first type of configuration isassociated with a first optical subcarrier assignment protocol; a secondtype of configuration for communicating with the optical communicationsnetwork according to a second bandwidth, where the second type ofconfiguration is associated with a second optical subcarrier assignmentprotocol, or a third type of configuration for communicating with theoptical communications network according to a third bandwidth, where thethird type of configuration is associated with a third opticalsubcarrier assignment protocol. The hub transceiver is also operable toassign, to each of the edge transceivers, a respective subset of theoptical subcarriers for use in communicating over the opticalcommunications network. Assigning the respective subset of the opticalsubcarriers includes, for each particular one of the edge transceivers,determining that the particular edge transceiver has the first type ofconfiguration, the second type of configuration, or the third type ofconfiguration; and in response to determining that the edge transceiverhas the first type of configuration, the second type of configuration,or the third type of configuration, assigning the respective subset ofthe optical subcarriers to the particular edge transceiver according toa particular one of the optical subcarrier assignment protocolsassociated with the determined type of configuration. The hubtransceiver is also operable to transmit, to each respective one of theedge transceivers, an indication of the respective subset of the opticalsubcarriers assigned to the particular edge transceiver.

In another aspect, a method includes determining, by a hub transceiver,a plurality of optical subcarriers available for assignment by the hubtransceiver to a plurality of the edge transceivers for use incommunicating over an optical communications network, where the hubtransceiver is communicatively coupled to a first network node and tothe optical communications network, and where each of the edgetransceivers is configured to be communicatively coupled to a respectivesecond network node and to the optical communications network. Each ofthe edge transceivers has one of: a first type of configuration forcommunicating with the optical communications network according to afirst bandwidth, where the first type of configuration is associatedwith a first optical subcarrier assignment protocol; a second type ofconfiguration for communicating with the optical communications networkaccording to a second bandwidth, where the second type of configurationis associated with a second optical subcarrier assignment protocol; or athird type of configuration for communicating with the opticalcommunications network according to a third bandwidth, where the thirdtype of configuration is associated with a third optical subcarrierassignment protocol. The method also includes assigning, by the hubtransceiver to each of the edge transceivers, a respective subset of theoptical subcarriers for use in communicating over the opticalcommunications network. Assigning the respective subset of the opticalsubcarriers includes, for each particular one of the edge transceivers:determining, by the hub transceiver, that the particular edgetransceiver has the first type of configuration, the second type ofconfiguration, or the third type of configuration; and in response todetermining that the edge transceiver has the first type ofconfiguration, the second type of configuration, or the third type ofconfiguration, assigning, by the hub transceiver, the respective subsetof the optical subcarriers to the particular edge transceiver accordingto a particular one of the optical subcarrier assignment protocolsassociated with the determined type of configuration. The method alsoincludes transmitting, by the hub transceiver to each respective one ofthe edge transceivers, an indication of the respective subset of theoptical subcarriers assigned to the particular edge transceiver.

Other implementations are directed to systems, devices, andnon-transitory, computer-readable media having instructions storedthereon, that when executed by one or more processors, cause the one ormore processors to perform operations described herein.

The details of one or more implementations are set forth in theaccompanying drawings and the description below. Other features andadvantages will be apparent from the description and drawings, and fromthe claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a diagram of an example of an optical communication system.

FIG. 1B shows block diagrams of primary node and secondary nodetransceivers illustrated in FIG. 1A.

FIGS. 2A-2C are diagrams of example data paths for communicating controlinformation in the optical communication system shown in FIG. 1 .

FIG. 3 is a diagram of example subcarriers of a communication channeland an out-of-band communication signal generated using an opticalcommunication system.

FIG. 4A is a diagram of an example transmitter module of an opticalcommunication system.

FIG. 4B is a diagram of an example of an amplitude modulation (AM)signal generator circuit.

FIG. 5 is a diagram of an example transmitter component of an opticalcommunication system.

FIG. 6A is a diagram of example devices for adjusting the gain of asignal generating using an example transmitter component.

FIG. 6B illustrates a portion of a primary node transmitter DSP ingreater detail consistent with an aspect of the present disclosure;

FIG. 6C illustrates a portion of a primary node transmitter DSP ingreater detail consistent with another aspect of the present disclosure;

FIG. 7 is a diagram of example devices of an example line systemcomponent in an optical communication system.

FIG. 8 is a diagram of example components of a receiver module of anoptical communication system.

FIG. 9A is a diagram of additional example components of a receivermodule of an optical communication system.

FIG. 9B is a diagram of example circuitry that may be provided in areceiver to output control information.

FIG. 9C is a diagram of an example shared laser.

FIG. 10 is a diagram of example subcarriers and multiple out-of-bandcommunication signals generated using an optical communication system.

FIG. 11 is a diagram of an X polarization and the Y polarization of anexample polarization shift keying (PolSK) out-of-band communicationsignal.

FIGS. 12A and 12B are diagrams of an example PolSK out-of-bandcommunication signal shifting from the X polarization to the Ypolarization.

FIG. 13 is a diagram of example devices of a transmitter component thatare used to generate a PolSK out-of-band communication signal fortransmitting control channel data.

FIG. 14 is a diagram of an example receiver component of an opticalcommunication system.

FIGS. 15 and 16 are diagrams of an example receiver component used togenerate PolSK out-of-band communication signal.

FIG. 17 is a diagram of example frequency bins associated with anout-of-band communication signal.

FIG. 18 is a diagram of an example optical communication system.

FIG. 19 is a diagram of an example amplitude modulation generatingcircuit.

FIG. 20 is a diagram of example circuitry for recovering controlinformation from signal supplied to a transceiver.

FIG. 21 is a diagram of an example process for configuring transceiversfor use on an optical communications network

FIG. 22A-22C are diagrams of an example technical for performing anoptical spectrum analysis.

FIGS. 22D and 22E are diagrams of an example power spectrum generatedbased on an optical spectrum analysis.

FIG. 23A is a diagram of an example broadcast transmission by a hubtransceiver.

FIG. 23B is a diagram of an example signal transmission by an edgetransceiver.

FIG. 23C is a diagram of an example signal reception by a hubtransceiver.

FIGS. 24A and 2B are diagrams of example optical subcarrier allotmenttechniques.

FIG. 25 is a diagram of using multiple optical subcarriers to mimic thepower signature of a legacy system.

FIG. 26 is a diagram of an example optical gateway.

FIG. 27 is a diagram of an example network topography for which powerbalancing may be used.

FIGS. 28A and 28B are state machine diagrams or flow diagram of phasesfor starting-up a transceiver . . . .

FIG. 29 is a diagram of an example process for dynamically configuring atransceiver as a hub transceiver or an edge transceiver.

FIGS. 30A and 30B are diagrams of an example transceiver that can beplugged into another network device.

FIGS. 31A-31F are flow chart diagrams of example processes that can beperformed using one or more of the systems described herein.

FIG. 32 is a diagram of an example computer system.

FIG. 33 is a diagram of example of circuitry for generating an opticalsubcarrier carrying data associated with a PRBS or blank packets.

FIG. 34 is a diagram of example circuitry for generating subcarriers andrespective amplitude modulations thereof.

FIG. 35 is a diagram of example time slots that can be assigned totransceivers for communication on an optical communications network.

Like reference numbers and designations in the various drawings indicatelike elements.

DETAILED DESCRIPTION

The present disclosure describes systems and methods for providingcontrol paths and/or communication paths to and from transceivers on anoptical communications network (e.g., transceivers that are installed inhost equipment or added to node equipment of the optical communicationsnetwork).

In some implementations, the systems and methods described herein canenable outside central software (e.g., central software implemented onone or more devices remote from the transceivers) to exchangeinformation with the transceivers directly. Accordingly, in at leastsome implementations, the central software can monitor and control thetransceivers independently of the host equipment or node equipment,and/or augment the control signals or communication signals that areprovided by the host equipment or the node equipment.

In some implementations, the system and methods described herein canenable transceivers to exchange information with one another directly.As a result, transceivers can communicate with one another to establishcontrol paths and/or communication path between them, and reconfigurethe control paths and/or communication paths dynamically (e.g., tocorrect for misconfigurations with respect to the network, to optimizethe performance of the transceivers, etc.). In some implementations,this process can be performed by the transceivers, independent of thecentral software, the host equipment, and/or the node equipment.

In some implementations, the data paths disclosed herein can also enablea line system component near a hub (or edge) node to send information toand receive information from a transceiver located in the hub (or edge)node directly, without access through the node equipment. Moreover, thedata paths disclosed herein can also facilitate the exchange of controland management information between transceivers, such as transceiversprovided in hub and edge nodes. Further, because the data paths areindependent of the node equipment, bi-directional communication ofcontrol information can occur simultaneously without direct coordinationbetween the transceivers and the node equipment. Accordingly, customerscan combine transceivers or transceiver modules and node equipment fromdifferent vendors to optimize performance and/or minimize costs.

The data paths can be realized through several example mechanisms thatreduce or prevent interference between the data paths. In one example, afirst data path between line system components and the transceivers canbe implemented with a low rate amplitude modulated signal that issuperimposed on high data rate optical signal output from thetransceivers. In addition, a second data path can be implemented throughpolarization modulation (e.g., polarization shift keying) of an opticalsignal that is also output from the transceiver.

In a further example, control information can be exchanged over a firstdata path between a transceiver (e.g., a hub or edge transceiver) and aline system component by way of a first amplitude modulation over afirst band of frequencies or at a first frequency. The first amplitudemodulation can superimposed on optical signals output from thetransceiver module. The second data path can implement, for example, bya second amplitude modulation over a second band of frequencies or asecond frequency. The second amplitude modulation can be furthersuperimposed on the optical signals output from the transceiver alongwith the first amplitude modulation. The second amplitude modulationfacilitates communication over a data path, for example, betweentransceivers.

In a further example, control information can be exchanged directlybetween a transceiver and central software through the transceiver'shost node over a management virtual local area network (VLAN) channel.In this example, the transceiver receives and sends packets with VLANtags with a central software entity. The host node configuration ofVLANs directs the management VLAN packets to the transceiver enablingthe transceiver to be the source and destination of these managementVLAN packets. In some implementations, this configuration does notrequire any line system components.

Example data paths and uses for those data paths are discussed ingreater detail below and shown in the drawings. For instance, FIGS. 1and 2A-2C show examples of data path connections can be establishedbetween devices on an optical communications network. Further, FIGS.3-17 show examples implementations in which transceivers or transceivermodules communicate control information or data with each other (e.g.,by way of a polarization modulated optical signal) and communicate withline system components, such as an optical gateway (e.g., by way ofamplitude modulation of the optical signals output from thetransceiver). Further, FIGS. 18-20 show example implementations in whichdata path connections are established by amplitude modulating theoptical signals that are output from the transceiver at differentfrequencies associated with different components in an opticalcommunication system. For example, an amplitude modulation at a firstfrequency or over a first band of frequencies can be associated withcommunication between a primary or hub node and a line system componentin a first direction, an amplitude modulation at a second frequency orover a second band of frequencies can be associated with communicationbetween a primary node and one or more secondary or edge nodes in thefirst direction, and an amplitude modulation at a third frequency orover a third band of frequencies can be associated with communicationbetween a line system component and one or more secondary or edge nodesin the first direction. Such communication in the first direction may becarried out on a first optical communication path. Further, FIGS. 21-35show example implementations for configuring network devices (e.g.,transceivers, optical gateways, and/or other devices) on an opticalcommunication system.

In a further example, an amplitude modulation at the first frequency orover the first band of frequencies can be associated with communicationbetween a secondary or edge node and a line system component in a seconddirection, an amplitude modulation at the second frequency or over asecond band of frequencies can be associated with communication betweenone or more secondary node or edge nodes and the hub or primary node inthe second direction, and an amplitude modulation at the third frequencyor over the third band of frequencies can be associated withcommunication between a line system component and the primary or hubnode in the second direction. Such communication in the second directioncan be carried out on a second optical communication path.

I. Example Data Paths

Before describing the above noted data paths, an example opticalcommunication system in which such data paths may be provided isdescribed below. In particular, FIG. 1A shows a block diagram of anexample optical communication system 100. The optical communicationsystem 100 includes, for example, a primary node 102, such as a router.A primary transceiver or transceiver module 106, for example, isprovided in the primary node 102 that supplies a downstream signal (DS)to an optical fiber link 115-1 (e.g., part of a first or downstreamoptical communication path), and receives an upstream signal (US) froman optical fiber links 115-2 (e.g., part of a second or upstream opticalcommunication path). In some implementations, a primary transceiver orprimary transceiver module may be referred to as a hub transceiver orhub transceiver module. The downstream optical signal DS is fed by afiber link 115-1 to an optical line system component, such as an opticalgateway OGW 103-1. As discussed in greater detail below with referenceto FIG. 3 , the optical signals DS and US each include a plurality ofoptical subcarriers, such as Nyquist optical subcarriers. The OGW 103-1also supplies the signal US on a fiber link 115-2 to a primarytransceiver 106.

As described below with reference to FIG. 7 the OGW 103-1 includesoptical and electrical components that extract control channelinformation carried by the signal DS and supply such information to acentral software 111, which may run on a network management system 109,including one or more computers and/or processors. As shown in FIG. 1A,a link 116-1 may supply such control information to the central software111. As further described below with reference to FIG. 7 , additionalcontrol information may be provided over a link 116-2 to the OGW 103-1,such that the optical and electrical circuitry in OGW 103-1 furtheroutputs the signal US with such additional control information fordetection by the transceiver 106.

The OGW 103-1 outputs the signal DS to one or more optical links, linesystem components (e.g., one or more optical amplifiers, such as erbiumdoped optical amplifiers), wavelength selective switches (WSSs), powersplitters and/or combiners, and optical multiplexers and/ordemultiplexers (e.g., an arrayed waveguide grating). Such components arerepresented in FIG. 1A by a sub-system 105. After propagating throughthe sub-system 105, the signal DS is supplied, for example, to anotheroptical gateway (OGW) 103-2, which, in this example, may include anoptical splitter in addition to the components or devices shown in FIG.7 . Accordingly, the OGW 103-2 may provide a power split portion of thesignal DS (e.g., DS′-1 to DS′-n) to a respective one of secondarytransceivers 108-1 to 108-n. Each of the secondary transceivers 108-1 to108-n is provided in a respective one of the secondary nodes 104-1 to104-n, and at least one of the transceivers is coupled to a terminal endof the downstream optical communication path. In some implementations, asecondary transceiver or secondary transceiver module may be referred toas an edge transceiver, edge transceiver module, leaf transceiver, orleaf transceiver module. Each secondary node 104 may have a structuresimilar to the primary node 102 and may operate in a manner similar tothat described above with respect to the primary node 102.

The OGW 103-2 may operate in a manner similar to that described abovewith respect to the OGW 103-1 to supply control information on a link117-1 to the control software 111 and to separately supply the same ordifferent control information to the secondary transceivers 108. Inaddition, the OGW 103-2 may operate in a manner similar to that of theOGW 103-1 to receive control information from the central software 111via a link 117-2, and separately receive the same or different controlinformation from the transceivers 108. The links 117-1 and 117-2 maycarry the same type of signals as the links 116-1 and 116-2.

As further shown in FIG. 1A, each secondary transceiver 108 may have astructure similar to and operate in manner similar to that describedabove with respect to the primary node 106. In one example, however,each of the secondary transceivers 108 may supply a modulated opticalsignal US′-1 to US′-n in an upstream direction. Each such optical signalmay include one or more optical subcarriers. Collectively, a number theoptical subcarriers output from the secondary transceivers 108 may beequal to, less than, or greater than the number of optical subcarriersoutput from the primary transceiver 106.

The optical signals US′-1 to US′-n may be combined by a combiner in theOGW 103-2, and output to the sub-system 105 in combined form as theupstream optical signal US. The optical signal US may then be providedto the OGW 103-2, which outputs the optical signal US onto a fiber link115-2, which supplies the optical signal US to the primary transceiver106.

FIG. 1B illustrates primary node 110 in greater detail. Primary node 106may include a transmitter 202 that supplies a downstream modulatedoptical signal including subcarriers, and a receiver that 204 that mayreceive upstream subcarriers carrying data originating from thesecondary nodes, such as nodes 108-1 to 108-n. Transmitter 202 andreceiver 204, in one example, collectively constitute a primary node orhub node transceiver.

FIG. 1B further shows a block diagram of one of secondary nodes 108,which may include a receiver circuit 302 that receives one or moredownstream transmitted subcarriers, and a transmitter circuit 304 thattransmits one or more subcarriers in the upstream direction.Collectively, receiver circuit 302 and transmitter circuit 304constitute a secondary node or edge node transceiver

Details of the transmitters and receivers of the hub and edge nodetransceivers are presented below with reference to FIGS. 4A, 4B, 5, 6A,6B, 6C, 8, and 9A-9C. It is understood that the hub and edge nodereceivers have a similar structure and operate in a similar manner.Also, the hub and edge node transmitters have a similar structure andoperate in a similar manner.

FIG. 2A shows the system 100 labeled with various data paths. Forexample, a data path CC1 provides communication of control informationbetween the OGW 103-1 and the primary transceiver 106. Data paths CC2and CC2′ facilitate control information communication between the OGW103-1 and the OGW 103-2, respectively, and the central software 111. Inaddition, a data path CC3 provides communication of control informationbetween one or more secondary transceivers 104 and the primarytransceiver 106, and, further, a data path CC1′ provide controlinformation between the OGW 103-2 and the secondary transceivers 108. Asnoted above, the data paths disclosed herein may provide communicationbetween the central software 111 and the transceivers and need notprovide such communication with intervening node equipment, such as arouter. Although FIG. 2A shows a first optical gateway (103-1) and asecond optical gateway (103-2), it is understood that, in anotherexample, only one such optical gateway may be provided near the primarynode 102, such that only the OGW 103-1 is included in the system 100. Inthat case, the OGW 103-2 can be replaced with an opticalsplitter/combiner, as discussed below with reference to FIGS. 2B and 2C.Alternatively, the OGW 103-1 may be replaced with a splitter/combiner,such that, in a further example, the system 100 only includes the OGW103-2 near the secondary nodes 104.

FIG. 2B shows an example of an idealized data path CC5 between thesecondary transceiver 108-n and the central software 111. As notedabove, in some implementations, due to incompatibilities between thetransceivers and the host node equipment, the data path CC5 cannot bemade directly to the transceiver 108-n. Here, the OGW 103-2 is replacedby a splitter/comber 137 (a line system component). Accordingly, datapath connections by which control information may be communicatedbetween the transceiver 108-n, the central software 111, and the networkmanagement system 109 will next be described with reference to FIG. 2C.

As shown in FIG. 2C, communication of control information between thesecondary transceiver 108-n and the central software 111 can be madethrough a data path CC3 (e.g., extending through the OGW 103-1 and theOGW 103-2), a data path CC4 through the transceiver 106, a data path CC1to the OGW 103-1, a data path CC3 through the OGW 103-1, and a data pathCC2 to the central software 111. As a result, communication of controlinformation between the central software 111 and the secondarytransceiver 108-n may be made independent of the node equipment in thesecondary node 104-n. Rather, in this example, such communication ismade through upstream transmission through the line system components,the transceiver 106, and the downstream transmission to the OGW 103-1,which outputs the control information to the central software 111 andthe network management system 109.

Alternatively, in some implementations, the secondary transceiver 108-nand the central software 111 can be directly connected with one anotherby the data path CC5. Accordingly, in those implementations, controlinformation may be communicated between the transceiver 108-n and thecentral software 111 directly (e.g., without being first relayed throughthe primary transceiver 106 and/or any OGWs). In some implementations,the data path CC5 can be implemented, at least in part, using a VLAN.

Similarly, as shown in FIG. 2B, in some implementations, the primarytransceiver 106 and the central software 111 can be directly connectedwith one another by a data path CC6. Accordingly, in thoseimplementations, control information may be communicated between theprimary transceiver 106 and the central software 111 directly (e.g.,without being first relayed through any OGWs). In some implementations,the data path CC6 can be implemented, at least in part, using a VLAN.

A first example of a data path implementation will next be describedwith reference to FIGS. 3-17 . In the first example, groups of opticalsubcarriers (e.g., Nyquist subcarriers) are amplitude modulated to carrycontrol information to/from the transceivers and the line systemcomponent (e.g., the optical gateway). Further, in the first example,additional control information is exchanged between the primarytransceiver and one or more secondary transceivers by modulating apolarization of an optical signal occupying a relatively narrowsspectrum, for example, between two spectrally adjacent opticalsubcarriers. A second example of a data implementation based onamplitude modulation at different frequencies is further described belowwith respect to FIGS. 18-20 .

II. First Data Path Implementation Example—Communication BetweenTransceiver and Line System Components Based on Amplitude Modulation

In some implementations, a two-way communications channel can beestablished between the devices of the optical communications network.As an example, a two-way communications channel can be establishedbetween two transceivers (e.g., a hub transceiver and an edgetransceiver). As another example, a two-way communications channel canbe established between a transceiver and an optical gateway.

As an example, FIG. 3 illustrates a plurality of subcarriers, SC1 to SC8that may be output by the transmitter of a transceiver. Each of thesubcarriers SC1 to SC8 may have a corresponding one of a plurality offrequencies f1 to f8. In addition, each of the subcarriers SC1 to SC8may be a Nyquist subcarrier. A Nyquist subcarrier is a group of opticalsignals, each carrying data, where (i) the spectrum of each such opticalsignal within the group is sufficiently non-overlapping such that theoptical signals remain distinguishable from each other in the frequencydomain, and (ii) such group of optical signals is generated bymodulation of light from a single laser. In general, each subcarrier mayhave an optical spectral bandwidth that is at least equal to the Nyquistfrequency, as determined by the baud rate of such subcarrier.

As discussed in greater detail below, the optical subcarriers SC1 to SC8are generated by modulating light output from a laser. The frequency ofsuch laser output light is f0 and is typically a center frequency suchthat half the subcarrier subcarriers (e.g., f5 to f8) are above f0 andhalf the subcarrier frequencies (e.g., f1 to f4) are below f0.

As further shown in FIG. 3 , the amplitudes of the subcarriers SC1 toSC8 may be collectively amplitude modulated together to vary theamplitude of each subcarrier between a first amplitude A1 and a secondlower amplitude A0. When the subcarriers SC1 to SC8 each have anamplitude A1, a ‘1’ bit, for example, is transmitted. On the other hand,when the subcarriers SC1 to SC8 each have an amplitude A0, a ‘0’ bit,for example, is transmitted. In this manner, amplitude modulation isemployed to transmit control information from the primary nodetransceiver 106, for example, to a line system component, as well asfrom the line system component to the primary node transceiver 106.Communication from a line system component to a secondary nodetransceiver 108 may be carried out by amplitude modulating an upstreamoptical signal (including subcarriers) at a line system component inaccordance with certain control information followed by transmitting apolarization modulated signal carrying such control information from theprimary node transceiver 106 to the secondary node transceiver 108.

Various mechanisms may be employed to amplitude modulate the opticalsubcarriers SC1 to SC8. Several examples of such mechanisms will next bedescribed. First, however, a description of the operation of atransmitter module 955 provided in the primary transceiver 106 will nextbe described with reference to FIGS. 4A, 4B, and 5 .

FIG. 4A is a diagram of an example transmitter 955 that can be included,for instance, in the primary transceiver 106 as transmitter 202 shown inFIG. 1B. It is understood that transmitters 302 in the secondarytransceivers 108 may have a similar configuration as that shown in FIG.4A. The transmitter 955 includes a digital signal processor 902including circuit blocks 903-1, 903-2, and 903-3. In this example, thecircuit block 903-1 receives first data including one or more of eightdata streams D1 to D8, each carrying user data or information. Such datais processed (e.g., as discussed in greater detail with respect to FIG.5 ), and the processed data is provided to the circuit block 903-3.Second data, including, for example, control information, CDPS, destinedfor a downstream transceiver (e.g., the transceivers 108) may be inputto the block 903-2, which processes such control information andsupplies the control information to the block 903-3. The circuit block903-3 is discussed in greater detail below with respect to FIGS. 15 and16 .

As further shown in FIG. 4A, the block 903-3 supplies digital signals todigital-to-analog conversion circuits 904-1 to 904-4 of a D/A and Opticsblock 901.

Each of the DACs 904 is operable to output second electrical signalsbased on the first electrical signals supplied by the Tx DSP 902. TheD/A and optics block 901 also includes modulator driver circuitry 906(“driver circuits 906”) corresponding to each of Mach-Zehnder modulatordrivers (MZMDs) 906-1, 906-2, 906-3, and 906-4. Each of the drivercircuits 906 is operable to output third electrical signals based on thesecond electrical signals output by each of the DACs 904.

The D/A and optics block 901 includes optical modulator circuitry 910(“modulator 910”) corresponding to each of the MZMs 910-1, 910-2, 910-3,and 910-4. Each of the modulators 910 is operable to supply or outputfirst and second modulated optical signals based on the third electricalsignals. The first modulated optical signal includes multiple opticalsubcarriers 300 carrying user data and is modulated to include controldata to be transmitted between nodes of the system 100, and the secondmodulated optical signal is, for example, polarization modulated, suchas polarization shift-keyed (PolSK), based on the second (control) data.Generation and detection of the second modulated optical signal isdescribed in further detail below with respect to FIG. 10 ).

Each of the modulators 910-1 to 910-4 of the D/A and optics block 901may be a Mach-Zehnder modulator (MZM) that modulates the phase and/oramplitude of the light output from a laser 908. As further shown in FIG.4A, a light beam output from the laser 908 (also included in the block901) is split such that a first portion of the light is supplied to afirst MZM pairing including the MZMs 910-1 and 910-2 and a secondportion of the light is supplied to a second MZM pairing including theMZMs 910-3 and 910-4.

The first portion of the light is further split into third and fourthportions, such that the third portion is modulated by the MZM 910-1 toprovide an in-phase (I) component of an X (or TE) polarization componentof a modulated optical signal, and the fourth portion is modulated bythe MZM 910-2 and fed to a phase shifter 912-1 to shift the phase ofsuch light by 90 degrees in order to provide a quadrature (Q) componentof the X polarization component of the modulated optical signal.

Similarly, the second portion of the light is further split into fifthand sixth portions, such that the fifth portion is modulated by the MZM910-3 to provide an I component of a Y (or TM) polarization component ofthe modulated optical signal, and the sixth portion is modulated by theMZM 910-4 and fed to a phase shifter 912-2 to shift the phase of suchlight by 90 degrees to provide a Q component of the Y polarizationcomponent of the modulated optical signal.

The optical outputs of the MZMs 910-1 and 910-2 are combined to providean X polarized optical signal including I and Q components and fed to apolarization beam combiner (PBC) 914 provided in the block 901. Inaddition, the outputs of the MZMs 910-3 and 910-4 are combined toprovide an optical signal that is fed to a polarization rotator 913,further provided in the block 901, that rotates the polarization of suchoptical signal to provide a modulated optical signal having a Y (or TM)polarization. The Y polarized modulated optical signal is also providedto a PBC 914, which combines the X and Y polarized modulated opticalsignals to provide a polarization multiplexed (“dual-pol”) modulatedoptical signal onto an optical fiber 916. In some examples, the opticalfiber 916 may be included as a segment of optical fiber in an exampleoptical communication path of the system 100.

In some implementations, the polarization multiplexed optical signaloutput from the D/A and optics block 901 includes the subcarriersSC0-SC8 (e.g., of FIG. 3 ), for example, such that each data subcarrier300 has X and Y polarization components and I and Q components.Moreover, each data subcarrier SC0 to SC8 may be associated with, orcorresponds to, a respective one of the outputs of the switches SW-1 toSW-8 associated with the DSP 902.

Next, several examples of amplitude modulation of the subcarriers SC1 toSC8 (see FIG. 3 ) will be described. As shown in FIG. 4A, each of thecontrol signals CDXI, CDXQ, CSYI, and CDYQ may be supplied to respectiveone of the Mach-Zehnder modulation driver circuits 906-1 to 906-4. Thesecontrol signals are indicative of control data to be communicated withthe line system components, and, based on these control signals, thedriver circuits 906 may further adjust the analog signals received fromthe DACs 904 in accordance with such control data, such that themodulators 910 are driven in such a manner as to collectively amplitudemodulate the subcarriers SC1 to SC8 to carry the control data.

In another example, a variable optical attenuator (VOA) 915 may beprovided to receive an optical signal including the subcarriers SC1 toSC8 output from the polarization beam combiner 914. The VOA 915 mayoperable to adjust or vary the attenuation of the subcarriers based on acontrol signal supplied thereto. By varying the attenuation experiencedby the optical subcarriers SC1 to SC8, the amplitude or intensity ofsuch subcarriers may be adjusted or controlled, such that thesubcarriers SC1 to SC8 are amplitude modulated to carry controlinformation based on the control signal supplied to the VOA 915.

A transmitter 955 (202 in FIG. 1B) may be provided in the module 917,which may also house a receiver portion (204 in FIG. 1B) of the primarytransceiver 106. Although the VOA 915 is shown inside the module 917, itis understood that the VOA 915 may be provided outside the module 917 toprovide amplitude modulation of the subcarriers SC1 to SC8 external tothe module 917.

In another example, amplitude modulation may be achieved by providing anamplitude modulation (AM) signal generator 992 which provides each ofoutputs AMO-1 to AMO-4 to a respective input of the DACs 904-1 to 904-4.These signals are generated in such a way that the DACs 904 outputanalog signals that include an amplitude modulation overlaying orsuperimposed on the data carrying DAC outputs. Based on such DACoutputs, the Mach-Zehnder modulator driver circuits (MZMDs) 906, inturn, output drive signal to the MZMs 910, as noted above. Accordingly,the combined MZM outputs supply optical subcarriers superimposed with anamplitude modulation based on the outputs of the signal generator 992(see also FIG. 3 ). Both X and Y polarization components, for example,of each optical subcarrier are subject to such amplitude modulation.

An AM signal generator portion 992 provides an input to the DAC 904-1and is shown in detail in FIG. 4B. In this example, the AM signalgenerator portion 992-1 receives control data CD1, which may bemultiplied, with a multiplier 440, by a cosine function, cos(ω_(AM)t),where ω_(AM) is indicative of a frequency of the amplitude modulationand t is time. The resulting product is output from the multiplier 440and provided to an adder circuit 442, which adds the number to theproduct output from the multiplier 440 to ensure that a positive numberis obtained. The output or sum of the adder 442 is next provided to amultiplier circuit 446, which multiplies such sum by another cosinefunction, cos(ω_(carrier)t), where ω_(carrier) is a carrier frequencyand t is time. In one example, ω_(carrier) is equal to zero. In otherexamples, ω_(carrier) is on the order of multiple GHz. The resultingproduct (AMO-1) is added or combined with a corresponding output of theDSP 902 and input to the DAC 904-1.

It is understood that circuitry similar to that shown in FIG. 4B is alsoincluded in the AM signal generator 992 to provide similar signals(AMO-2 to AMO-3) to the inputs of remaining the DACs 904-2 to 904-4. Asnoted above, based on such inputs, the MZMs 910 (collectively, the MZMsare also considered a modulator), output optical subcarriers that arecollectively amplitude modulated, as shown in FIG. 3 , to carry controlinformation. The example shown in FIG. 4B may be implemented as analternative to the other amplitude modulation examples described inconnection with FIG. 4A, as well as described below in connection withFIG. 6A.

FIG. 5 shows the DSP 902, including blocks 903-1 and 903-3, in greaterdetail. As noted above, the block 903-1 receives user data streams orinputs D1 to D8. A shown in FIG. 5 , each such data stream is suppliedto a respective one of the forward error correction (FEC) encoders1002-1 to 1002-8. The FEC encoders 1002-1 to 1002-8 carry out forwarderror correction coding on a corresponding one of the switch outputs,such as, by adding parity bits to the received data. The FEC encoders1002-1 to 1002-8 may also provide timing skew between the subcarriers tocorrect for skew introduced during transmission over one or more opticalfibers. In addition, the FEC encoders 1002-1 to 1002-8 may interleavethe received data.

Each of the FEC encoders 1002-1 to 1002-8 provides an output to acorresponding one of multiple bits to symbol circuits, 1004-1 to 1004-8(collectively referred to herein as “1004”). Each of the bits to symbolcircuits 1004 may map the encoded bits to symbols on a complex plane.For example, the bits to symbol circuits 1004 may map four bits to asymbol in a dual-polarization Quadrature Phase Shift Keying (QPSK) orand m-quadrature amplitude modulation (m-QAM, m being a positiveinteger) constellation, such as 8-QAM, 16-QAM, and 64-QAM. Each of thebits to symbol circuits 1004 provides first symbols, having the complexrepresentation XI+j*XQ, associated with a respective one of the datainput, such as D0, to a DSP portion 1003. Data indicative of such firstsymbols may carried by the X polarization component of each subcarrierSC0-SC8.

Each of the bits to symbol circuits 1004 may further provide secondsymbols having the complex representation YI+j*YQ, also associated witha corresponding one of the data inputs D0 to D8. Data indicative of suchsecond symbols, however, is carried by the Y polarization component ofeach of the subcarriers SC-1 to SC-8.

As further shown in FIG. 5 , each of the first symbols output from eachof the bits to symbol circuits 1004 is supplied to a respective one offirst overlap and save buffers 1005-1 to 1005-8 (collectively referredto herein as overlap and save buffers 1005) that may buffer 256 symbols,for example. Each of the overlap and save buffers 1005 may receive 128of the first symbols or another number of such symbols at a time from acorresponding one of bits to symbol circuits 1004. Thus, the overlap andsave buffers 1005 may combine 128 new symbols from the bits to symbolcircuits 1004, with the previous 128 symbols received from thebits-to-symbol circuits 1004.

Each overlap and save buffer 1005 supplies an output, which is in thetime domain, to a corresponding one of the fast Fourier Transform (FFT)circuits 1006-1 to 1006-8 (collectively referred to as “FFTs 1006”). Inone example, the output includes 256 symbols or another number ofsymbols. Each of the FFTs 1006 converts the received symbols to thefrequency domain using or based on, for example, a fast Fouriertransform. Each of the FFTs 1006 may include 256, for example, memoriesor registers, also referred to as frequency bins or points, that storefrequency components associated with the input symbols. Each of thereplicator components 1007-1 to 1007-8 may replicate the 256 frequencycomponents associated with of the FFTs 1006 and store such components in512 or another number of frequency bins (e.g., for T/2 based filteringof the subcarrier) in a respective one of the plurality of replicatorcomponents. Such replication may increase the sample rate. In addition,replicator components or circuits 1007-1 to 1007-8 may arrange or alignthe contents of the frequency bins to fall within the bandwidthsassociated with pulse shaped filter circuits 1008-1 to 1008-8 describedbelow.

Each of the pulse shape filter circuits 1008-1 to 1008-8 may apply apulse shaping filter to the data stored in the 512 frequency bins of arespective one of the plurality of replicator components 1007-1 to1007-8 to thereby provide a respective one of multiple filtered outputs,which are multiplexed and subject to an inverse FFT, as described below.The pulse shape filter circuits 1008-1 to 1008-8 calculate thetransitions between the symbols and the desired subcarrier spectrum sothat the subcarriers can be spectrally packed together for transmission(e.g., with a close frequency separation). The pulse shape filtercircuits 1008-1 to 1008-8 may also be used to introduce timing skewbetween the subcarriers to correct for timing skew induced by linksbetween nodes shown in FIG. 1 , for example. A memory component 1009,which may include a multiplexer circuit or memory, may receive thefiltered outputs from the pulse shape filter circuits 1008-1 to 1008-8,and multiplex or combine such outputs together to form an elementvector.

The output of the memory 1009 is fed to the block 903-3, which includes,in this example, an IFFT circuit or component 1010-1. The IFFT circuit1010-1 may receive the element vector and provide a corresponding timedomain signal or data based on an inverse fast Fourier transform (IFFT).In one example, the time domain signal may have a rate of 64 G Sample/s.A take last buffer or memory circuit 1011-1 may select the last 1024 oranother number of samples from an output of the IFFT component orcircuit 1010-1 and supply the samples to the DACs 904-1 and 904-2 at 64G Sample/s, for example. As noted above, the DAC 904-1 is associatedwith the in-phase (I) component of the X pol signal and DAC 904-2 isassociated with the quadrature (Q) component of the Y pol signal.Accordingly, consistent with the complex representation XI+jXQ, the DAC904-1 receives values associated with XI and the DAC 904-2 receivesvalues associated with jXQ. Based on these inputs, the DACs 904-1 and904-2 provide analog outputs to the MZMD 906-1 and the MZMD 906-2,respectively, as discussed above.

As further shown in FIG. 5 , each of the bits to symbol circuits 1004-1to 1004-8 outputs a corresponding one of symbols indicative of datacarried by the Y polarization component of the polarization multiplexedmodulated optical signal output on the optical communication path orfiber 916. As further noted above, these symbols may have the complexrepresentation YI+j*YQ. Each such symbol may be processed by arespective one of the overlap and save buffers 1015-1 to 1015-8, arespective one of the FFT circuits 1016-1 to 1016-8, a respective one ofthe replicator components or circuits 1017-1 to 1017-8, the pulse shapefilter circuits 1018-1 to 1018-8, and the multiplexer or memory 1019 ofblock the 903-1. Moreover, the output of the multiplexer or memory 1019may be fed to the block 903-3, which further includes a IFFT 1010-2, anda take last buffer or memory circuit 1011-2, to provide processedsymbols having the representation YI+j*YQ in a manner similar to or thesame as that discussed above in generating processed symbols XI+j*XQoutput from the take last circuit 1011-1. In addition, symbol componentsYI and YQ are provided to the DACs 904-3 and 904-4, respectively. Basedon these inputs, the DACs 904-3 and 904-4 provide analog outputs to theMZMD 906-3 and the MZMD 906-4, respectively, as discussed above.

In one example, described in greater detail below, block 903-3 alsoreceives outputs from block 903-2 as noted above and discussed ingreater detail below with respect to FIG. 13 . Block 903-2 may beoptionally provided to provided transmission of control signals by wayof an additional subcarrier which, in a further example, is polarizationmultiplexed. In the current example, however, when amplitude modulationis employed, such transmission may be omitted or provided in addition tothe amplitude modulation described herein.

While FIG. 5 shows the Tx DSP 902 as including a particular quantity andarrangement of functional components, in some implementations, the DSP902 may include additional functional components, fewer functionalcomponents, different functional components, or differently arrangedfunctional components. In addition, typically the number of overlap andsave buffers, FFTs, replicator circuits, and pulse shape filtersassociated with the X component may be equal to the number of datainputs, and the number of such circuits associated with the Y componentmay also be equal to the number of switch outputs. However, in otherexamples, the number of data inputs may be different than the number ofthese circuits. As noted above, based on the outputs of the MZMDs 906-1to 906-4, multiple optical subcarriers SC0 to SC8 may be output onto theoptical fiber 916.

A further example of circuitry that may be employed to allow theamplitude modulation subcarriers SC1 to SC8 to carry control informationwill next be described with reference to FIG. 6A. Here, a plurality ofmultiplier circuits 1020-1 to 1020-8, which may be complex multipliercircuits, are provided within the DSP 902, to receive a respective oneof outputs O1 to O8 from a corresponding one of the pulse shape filters1018-1 to 1018-8. Each of the multiplier circuits 1020-1 to 1020-8receives a corresponding one of gain parameters G1 to G8, such that, inthis example, each of the outputs O1 to O8 is multiplied by acorresponding one of the gain parameters G1 to G8. Each output O1 to O8is associated with a respective one of the subcarriers SC1 to SC8.Moreover, each is associated with a gain or amplitude of a respectiveone of the subcarriers. That is, the amplitude of each of the opticalsubcarriers SC1 to SC8 output from the optical modulators 910 may bebased on the gain parameters G1 to G8. Thus, by varying the gainparameters G1 to G8, the amplitude of the optical subcarriers SC1 to SC8may also be varied or modulated. The gain parameters G1 to G8, maytherefore be adjusted or controlled to amplitude modulate thesubcarriers SC1 to SC8, as shown in FIG. 8 , to carry controlinformation to the line system components.

In some implementations, the gain of each multiplier 1020 is softwareprogrammable (or may be implemented in firmware) along with a frequencyshaping function in a filter 1018 preceding the multiplexing performedby the multiplexer or memory 1019.

Preferably, in the example shown in FIG. 6A, the gain parameter changesor variations are synchronized to occur at the same time orsubstantially the same time so that the amplitudes of the subcarriersSC1 to SC8 vary at the same time or substantially the same time.Moreover, the above-described multiplier circuits 1020 may be includedin the DSP 902 to provide amplitude modulation of the Y polarizationcomponent of each of the subcarriers SC1 to SC8. It is understood thatsimilar multiplier circuits may be provided between the pulse shapefilters 1008 and the memory 1009 to provide corresponding amplitudemodulation of the X polarization component of each subcarrier SC1 toSC8.

As discussed in greater detail below, optical subcarriers may beselectively output by transceivers 106 and/or 108. Control signals maybe provided to such transceivers, as described herein, and controlinformation or data associated with or carried by such data, in oneexample, includes messages or instructions indicating the number ofoptical subcarriers to be output by each transceiver. The number ofoptical subcarriers that may be output, however, can vary over time inaccordance with bandwidth of data capacity requirements of thetransceiver. For example, if at one point in time, network bandwidthrequirements are such that transceivers 108-1 transmits 200 Gbit/s toprimary node transceiver 106, and, each subcarrier carries dataassociated with 100 Gbit/s transmission, transceiver 108-1 outputs twooptical subcarriers (2 subcarriers×100 Gbit/s).

As noted above, however, bandwidth requirements are often not static.Accordingly, in the current example, at another point in time, thenetwork capacity requirements may be such that transceiver 108-1transmits 100 Gbit/s to primary node transceiver 106. Controlinformation, as noted above, is therefore, provided to transceiver 108-1including instructions for transmitting one optical subcarrier, insteadof two. As a result, transceiver 108-1, turns off or cancels on of thesubcarriers that previously had been transmitted. On the other hand, if,for example, additional bandwidth or capacity is required to be outputfrom transceiver 108-1, further instructions may be provided to increasethe number of optical subcarriers output from transceiver 108-1. In asimilar manner control information may be provided to increase ordecrease, as required, the number of optical subcarriers output fromeach of transceiver 108. Similarly, instructions may be provided toprimary node transceiver 106 to increase or decrease the number ofoptical subcarriers output therefrom.

Example circuitry for adding optical subcarriers or reducing the numberof optical carriers output from transceivers 106 and 108 will next bedescribed with reference to FIGS. 6B and 6C.

As noted above, FFTs 1006 and 1016 include a plurality of bins, alsoreferred to frequency bins, which, in one example, are memories orregisters storing frequency components generated by the FFTs. Selectedfrequency bins FB are shown in FIG. 6B. Groups of such frequency bins FBare associated with given optical subcarriers. Accordingly, for example,a first group of frequency bins, FB1-0 to FB1-n, is associated withoptical subcarrier SC1 and a second group of frequency bins FB8-0 toFB8-n with SC8 (where n is a positive integer). As further shown in FIG.10 b , each of frequency bins FB is further coupled to a respective oneof switches SW. For example, each of frequency bins FB1-0 to FB1-n iscoupled to a respective one of switches SW1-0 to SW1-n, and each ofFB8-0 to FB8-n is coupled to a respective one of switches or switchcircuits SW8-0 to SW8-n.

Each switch SW selectively supplies either frequency domain data outputfrom one of FFT circuits 1006-1 to 1006-8 or a predetermined value, suchas 0. In order to block or eliminate transmission of a particularsubcarrier, the switches SW associated with the group of frequency binsFB associated with that subcarrier are configured to supply the zerovalue to corresponding frequency bins. Accordingly, for example, inorder to block subcarrier SC1, switches SW1-0′ to SW1-n′ supply zero (0)values to a respective one of frequency bins FB1-0 to FB1-n. Furtherprocessing, as described below, of the zero (0) values by replicatorcomponents 1007 as well as other components and circuits in DSP 902result in drive signals supplied to modulators 910, such that subcarrierSC1 is omitted from the optical output from the modulators. As a result,optical subcarriers may be removed or cancelled so that the number ofoptical subcarriers is reduced.

On the other hand, switches SW′ may be configured to supply the outputsof FFTs 1006, i.e., frequency domain data FD, to corresponding frequencybins FB. Further processing of the contents of frequency bins FB byreplicator components 1007 and other circuits in DSP 902 result in drivesignals supplied to modulators 910, whereby, based on such drivesignals, optical subcarriers are generated that correspond to thefrequency bin groupings associated with that subcarrier. In this way,optical subcarriers may be added, so that the number of opticalsubcarriers may be increased.

In the example discussed above, switches SW1-0′ to SW1-n′ supplyfrequency domain data FD1-0 to FD1-n from FFT 1006-1 to a respective oneof switches SW1-0′ to SW1-n.′ These switches, in turn, supply thefrequency domain data to a respective one of frequency bins FB1-0 toFB1-n for further processing, as described in greater detail above.

In a further example, a corresponding one of pulse shape filters 1008-1to 1008-8 may selectively generate zeroes or predetermined values that,when further processed, also cause one or more subcarriers SC to beomitted from the output of either primary node transmitter 202 orsecondary node transmitter 304. In particular, as shown in FIG. 10 c ,pulse shape filters 1008-1 to 1008-8 are shown as including groups ofmultiplier circuits M1-0 to M1-n . . . M8-1 to M8-n (also individuallyor collectively referred to as M). In one example, each multipliercircuit M constitutes part of a corresponding butterfly filter. Inaddition, in another example, each multiplier circuit grouping isassociated with a corresponding one of subcarriers SC.

Each multiplier circuit M receives a corresponding one of outputgroupings RD1-0 to RD1-n RD8-0 to RD8-n from replicator components 1007.In order to remove or eliminate one of subcarriers SC, multipliercircuits M receiving the outputs within a particular grouping associatedwith that subcarrier multiply such outputs by zero (0), such that eachmultiplier M within that group generates a product equal to zero (0).The zero products then are subject to further processing similar to thatdescribed above to provide drive signals to modulators 910 that resultin a corresponding subcarrier SC being omitted from the output of thetransmitter (either transmitter 202 or 304).

On the other hand, in order to provide or add a subcarrier SC, each ofthe multiplier circuits M within a particular groping may multiply acorresponding one of replicator outputs RD by a respective one ofcoefficients C1-0 to C1-n . . . C8-0 to C8-n, which results in at leastsome non-zero products being output. Based on the products output fromthe corresponding multiplier grouping, drive signals are provided tomodulators 910 to output the desired subcarrier SC from the transmitter(either transmitter 202 or 304).

Accordingly, for example, in order to block or eliminate subcarrier SC1,each of multiplier circuits M1-0 to M1-n (associated with subcarrierSC1) multiplies a respective one of replicator outputs RD1-0 to RD1-n byzero (0). Each such multiplier circuit, therefore, provides a productequal to zero, which is further processed, as noted above, such thatresulting drive signals cause modulators 910 to provide an opticaloutput without SC1. In order to reinstate SC1, multiplier circuits M1-0to M1-n multiply a corresponding one of appropriate coefficients C1-0 toC1-n by a respective one of replicator outputs RD1-0 to RD1-n to provideproducts, at least some of which are non-zero. Based on these products,as noted above, modulator drive signals are generated that result insubcarrier SC1 being output. Other subcarriers may be added or removedat each secondary node and the primary node in a similar manner as thatdescribed above.

The above examples are described in connection with generating orremoving the X component of a subcarrier SC. The processes and circuitrydescribed above is employed or included in DSP 902 and optical circuitryused to generate the Y component of the subcarrier to be blocked. Forexample, switches and bins circuit blocks 1022-1 to 1022-8, have asimilar structure and operate in a similar manner as switches and binscircuit blocks 1021 described above to provide zeroes or frequencydomain data as the case may be to selectively block the Y component ofone or more subcarriers SC. Alternatively, multiplier circuits, likethose described above in connection with FIG. 10 c may be provided tosupply zero products output from selected pulse shape filters 1018 inorder to block the Y component of a particular subcarrier or, ifnon-zero coefficients are provided to the multiplier circuits instead,generate the subcarrier.

Thus, the above examples illustrate mechanisms by which subcarriers SCmay be selectively blocked from or added to the output of transmitter202. Since, as discussed below, DSPs and optical circuitry provided insecondary node transmitters 304 are similar to that of primary nodetransmitter 202, the processes and circuitry described above isprovided, for example, in the secondary node transmitters 304 toselectively add and remove subcarriers SC′ from the outputs of thesecondary node transmitters, as described in connection with FIGS. 13b-13 k . Moreover, consistent with the present disclosure, the circuitrydescribed above in connection with FIGS. 10 b and/or 10 c may beconfigured so that a first number of optical subcarriers are output fromthe transmitter (in either the primary node transceiver 106 or thesecondary node transceivers 108) during a first period of time based oninitial capacity requirements. Later, during a second period of time, asecond number of optical subcarriers can be output from the hub and/orleaf transmitters based on capacity requirements different than thefirst capacity requirements.

In a further example, control circuit 1161 (discussed below inconnection with FIGS. 9A and 9B) may provide signals, based oninstructions associated with the AM modulated signals noted above, tocontrol switches SW′ to supply either zeros or frequency domain data, asnoted above. Alternatively, control circuit 1161 may provide, based onalternative instructions associated with the AM modulated signals,either the coefficients or zeros noted above for adding or removingoptical subcarriers. Thus, in one example, the control information ordata received by control circuit 1161 may be indicative of the number ofoptical subcarriers to be output from a transceiver housing or includingcontrol circuit 1161.

Reception and transmission of control information at a line systemcomponent, such as the optical gateway (OGW) 103-1 will next bedescribed with reference to FIG. 7 . As noted above, the techniquesdescribed herein are used to provide communications between a hub orprimary node 102 using amplitude modulation (AM) of the subcarriers SC1to SC8.

As shown in FIG. 7 , the OGW 103-1 generally includes a microprocessoror DSP 702, a line system data generator 704, a digital-to-analogconversion circuit 706 (“DAC 706”), and one or more variable opticalattenuators (VOAs) 708-1, 708-2. In some implementations, one or more ofthe components of the OGW 103-1 can be placed at various locations alongan optical communication path between an example primary or hub node 102and an example secondary or edge node 104 of the system 100. Forexample, one or more of the components of the OGW 103-1 can be placedadjacent to a splitter/combiner or in between two distinct splittersthat are each intermediate a primary node 102 and a secondary node 104.The OGW 103-1 may also be provided adjacent an optical amplifier.

Transmission of control information from the OGW 103-1 to eithertransceiver 106 or one of the transceivers 108 will next be described.Control information is provided based on the status of the line systemcomponent or other information associated with the line systemcomponent. Such information may include operations, administration,maintenance, and provisioning (OAM&P) information, such as, if the linesystem component is adjacent an optical amplifier, the gain of theamplifier or which optical signals (by wavelength) are input to theamplifier. Alternatively, the control information may include anindication of which optical signals and subcarriers are input to/outputfrom specified ports of a WSS. Such information may be supplied tocircuitry in the microprocessor or microcontroller 702 referred to as aline system data generator 704, which control data that is to betransmitted to a near end transceiver, for example. The line systemgenerator may provide the control data based on measured parametersassociated with the optical communication path or fiber links 705 and/or703, for example. Alternatively, control information may be supplied tothe line system generator 704 by the central software 111. In a furtherexample, control information may be supplied directly from the centralsoftware to the DAC 706. In any event, the OGW 103-1 typically transmitscontrol information to the transceiver closest to it, namely the primarytransceiver 106. The OGW 103-2, having a similar construction as the OGW103-1, transmits control information to one or more of the transceivers108, which are closest to the OGW 103-2.

The line system data generator 704 may supply the control information asa digital or binary electrical signal to a digital-to-analog conversioncircuit 706, which converts the received signal to an analog signalindicative of the control information to be transmitted. The analogsignal is then provided to a variable optical attenuator (VOA) 708-2,for example via an optical input port 718-1 (e.g., an interface forreceiving optical signals). The VOA 706-2 may also receive an opticalsignal including a plurality of the subcarriers SC1′ to SC8′, eachhaving a corresponding one of the frequencies f1′ to f8′, for examplevia an optical input port 718-2. In this example, the subcarriers SC1′to SC8′ are transmitted from one or more of the secondary transceivers108 on an optical fiber or optical communication path 703. Based on theanalog signal received via the input port 718-1, the VOA 708-2collectively adjusts the attenuation, and thus the amplitude orintensity, of subcarriers SC1′ to SC8′ based on the control information.As a result, the subcarriers SC1′ to SC8′ are amplitude modulated tocarry such control information to a receiver in either the primarytransceiver 106 or a receiver in one or more of the secondarytransceivers 108.

Detection of an optical signal including amplitude modulated subcarrierstransmitted on an optical communication path 705 from a near endtransceiver, such as the subcarriers SC1 to SC8 transmitted from primarynode transceiver 106, will next be described. The optical signal isinput to an optical tap 710, which may provide an optical power splitportion of the optical signal (e.g., 1% to 10%) to a photodiode circuit711. A remaining portion of the optical signal continues to propagatealong optical communication path 705. A VOA 708-1 may optionally beprovided for power balancing. For example, the VOA 708-1 can receive thesignal output by the optical tap 710 via an optical input port 720-1,and attenuate the signal according to an analog signal 722 received viathe optical input port 720-2 (e.g., control information received from onmore sources).

As further shown in FIG. 7 , the tapped portion of the optical signal isconverted by the photodiode circuit 711 to a corresponding analogelectrical signal (e.g., a voltage or a current). The analog signal isfed to an analog-to-digital conversion circuit 712, which suppliesdigital signals based on the received analog signal. Such digitalsignals are optionally provided to a bandpass pass filter 714 and thenoutput to a conventional clock and data recovery circuitry 716, whichoutputs the control information to the central software 111, for exampleby way of an optical signal (e.g., an optical service channel (OSC)), orby way of an electrical signal (e.g., an Ethernet signal).

A parameter associated with line system component may be adjusted orcontrolled based on the received control information. For example, ifthe line system component includes an optical amplifier, such as anerbium doped fiber amplifier, the control information may includeinstructions or other data for adjusting a gain of the opticalamplifier. Alternatively, or in addition, the control information mayinclude information for adjusting an attenuation of the VOA 708-1.

Detection of amplitude modulated subcarriers output from the OGW 103-1will next be described with reference to FIGS. 8 and 9A, which show anoptical receiver that may be provided in the primary transceiver 106 asreceiver 204 in FIG. 1B or one or more of the secondary transceivers 108as receiver 304. It is understood that the structure and operation ofthe OGW 103-2 is similar to that of the OGW 103-1. The module 1155 isincluded as a receiver in the transceiver 106, for example. It isunderstood that the transmitter and receiver provided in the secondarytransceivers 108 may have a similar structure and operate in a similarmanner as the transmitter and receiver provided in the primarytransceiver 106. That is, such transmitters in both the primary and thesecond transceivers may have structure similar to or the same as thetransmitter 955 and the receiver module 1155, respectively.

Referring now to FIG. 8 , the optical receiver 1100 of the receivermodule 1155 may include a receiver (Rx) optics and A/D block 1100,which, in conjunction with a Rx DSP 1150, may carry out coherentdetection. The block 1100 may include a polarization splitter 1105 withfirst and second outputs, a local oscillator (LO) laser 1110, such as asemiconductor laser, 90 degree optical hybrids or mixers 1120-1 and1120-2 (referred to generally as hybrid mixers 1120 and individually ashybrid mixer 1120), detectors 1130-1 and 1130-2 (referred to generallyas detectors 1130 and individually as detector 1130, each includingeither a single photodiode or balanced photodiode), and AC couplingcapacitors 1132-1 and 1132-2. A frequency control circuit 1107 may beprovided to adjust or control a frequency of light output form LO laser1110, as well as shared laser 908 described below (FIG. 9C), based onsignal output from DSP 1150. In one example, frequency control circuit1107 may include a heater provided adjacent laser 1110 or 908, thetemperature of which, as well as the laser, being controlled based on anoutput from DSP 1150. In another example, frequency control circuit 1107may include a circuitry that controls the amount of current supplied tothe laser. The frequency of light output from laser 1110 or 908 istypically a function of the temperature of the laser as well as thecurrent supplied to the laser. Thus, by controlling the temperatureand/or the current supplied to the laser, the frequency of the lightoutput from laser 1110 may also be adjusted. In a further example,circuit 1161, described below may provide signals for controlling thefrequency of laser 1110 or laser 908.

In one example, one laser may be provided that is “shared” between thetransmitter and receiver portions in the transceivers 106 and/or thetransceivers 108. For example, a splitter 999 can provide a firstportion of light output from the laser 908 to the MZMs 910 in thetransmitter portion of the transceiver. Further, the splitter 999 canprovide a second portion of such light acting as a local oscillatorsignal fed to 90 degree optical hybrids 1120 in the receiver portion ofthe transceiver, as shown in FIG. 9C. In this example, the laser 1110may be omitted.

The block 1100 also includes trans-impedance amplifiers/automatic gaincontrol circuits 1134 (“TIA/AGC 1134”) corresponding to the TIA/AGC1134-1 and 1134-2, analog-to-digital conversion circuitry 1140 (“ADC1140”) corresponding to the ADCs 1140-1 and 1140-2, and an Rx DSP 1150.The ADCs 1140-1 and 1140-2 may be referred to generally as the ADCs 1140and individually as the ADC 1140.

The polarization beam splitter (PBS) 1105 may include a polarizationsplitter that receives an input polarization multiplexed optical signalincluding the optical subcarriers SC0 to SC8 supplied by an opticalfiber link 1101, which may be, for example, an optical fiber segment aspart of one of optical communication paths of the system 100. The PBS1105 may split the incoming optical signal into the two X and Yorthogonal polarization components. The Y component may be supplied to apolarization rotator 1106 that rotates the polarization of the Ycomponent to have the X polarization. Hybrid mixers 1120 may combine theX and rotated Y polarization components with light from a localoscillator laser 1110. For example, the hybrid mixer 1120-1 may combinea first polarization signal (e.g., the component of the incoming opticalsignal having a first or X (TE) polarization output from a first port ofthe PBS 1105) with light from the local oscillator laser 1110, and thehybrid mixer 1120-2 may combine the rotated polarization signal (e.g.,the component of the incoming optical signal having a second or Y (TM)polarization output from a second port of the PBS 1105) with the lightfrom the local oscillator laser 1110.

The detectors 1130 may detect mixing products output from the opticalhybrids, to form corresponding voltage signals, which are subject to ACcoupling by the capacitors 1132-1 and 1132-2, as well as amplificationand gain control by the TIA/AGCs 1134-1 and 1134-2. In someimplementations, the TIA/AGCs 1134 are used to smooth out or correctvariations in the electrical signals output from the detector 1130 andthe AC coupling capacitors 1132. Accordingly, in one example, since theamplitude modulation of the received subcarriers may manifest itself assuch variations, the control information associated with such amplitudemodulation may be derived based on the magnitude or the amount ofcorrection of such electrical signals. Accordingly, as shown in FIG. 8 ,line system control data may be output from the TIA/AGC circuits.

As further shown in FIG. 8 , the outputs of the TIA/AGCs 1134-1 and1134-2 are supplied to the ADCs 1140, which convert the outputs of theTIA/AGCs, which are analog voltage signals, for example, to digitalsamples or digital signals. Namely, two detectors or photodiodes 1130-1may detect the X polarization signals to form the corresponding voltagesignals, and a corresponding two ADCs 1140-1 may convert the voltagesignals to digital samples associated with the first polarizationsignals after amplification, gain control and AC coupling. Similarly,two detectors 1130-2 may detect the rotated Y polarization signals toform corresponding voltage signals, and a corresponding two ADCs 1140-2may convert such voltage signals to digital samples associated with thesecond polarization signals (Y polarization) after amplification, gaincontrol and AC coupling. The Rx DSP 1150 may process the digital samplesassociated with the X and Y polarization components to the output dataD0 to D8 associated with the subcarriers SC1 to SC8.

While FIG. 8 shows optical receiver 1100 as including a particularquantity and arrangement of components, in some implementations, theoptical receiver 1100 may include additional components, fewercomponents, different components, or differently arranged components.The quantity of the detectors 1130 and/or ADCs 1140 may be selected toimplement an optical receiver 1100 that is capable of receiving apolarization-multiplexed signal. In some instances, one of thecomponents illustrated in FIG. 8 may carry out a function describedherein as being carry outed by another one of the components illustratedin FIG. 8 .

Consistent with the present disclosure, in order to demodulate thesubcarriers SC0 to SC8, the local oscillator laser 1110 may be tuned tooutput light having a wavelength or frequency relatively close to one ormore of the subcarrier wavelengths or frequencies to thereby cause abeating between the local oscillator light and the subcarriers.

In one example, the local oscillator laser may be a semiconductor laser,which may be tuned thermally or through current adjustment. If thermallytuned, the temperature of the local oscillator laser 1110 is controlledwith a thin film heater, for example, provided adjacent the localoscillator laser. Alternatively, the current supplied to the laser maybe controlled, if the local oscillator laser is current tuned. The localoscillator laser 1110 may be a semiconductor laser, such as adistributed feedback laser or a distributed Bragg reflector laser.

Alternatively, control information carried by the above theabove-described amplitude modulation may also be detected with a meansquare detector (“MSD”) circuit 1160 discussed in greater detail withrespect to FIG. 9A. For example, the MSD 1160 is coupled to theanalog-to-digital conversion circuitry (ADCs 1140) and is operable toreceive digital samples received from the ADCs 1140 and output suchdigital samples to the RX DSP 1150. The MSD circuit 1160 is configuredto measure the average power of the received signal. In one example, theaverage power is calculated by summing the squares of the in-phase andquadrature components of both the X and Y polarizations (averagepower=I_(X) ²+Q_(X) ²+I_(Y) ²+Q_(Y) ²). In a further example, Ix, Qx,are the outputs of the ADCs 1140-1 and Iy, Qy are the outputs of theADCs 1140-2. A low pass filter may be provided if high AM frequenciesare employed.

By calculating the average power, as noted above, changes in suchaverage power may also be determined and interpreted as theabove-described amplitude modulation. Conventional processing of suchamplitude modulation, optionally within the MDS circuit 1160, may beemployed to provide a control (“CS” in FIG. 9A) associated with suchamplitude modulation. Such CS, in turn, may be processed to providecontrol information or data to a control circuit 1161 (see FIG. 9B), asdescribed below.

As shown in FIG. 9B, in order to supply control data or informationbased on the outputs from either the TIA/AGC circuits 1134 or the meansquare detector 1160, the outputs from either circuit are provided to abandpass filter (BPF) 1182, for example, which passes frequencycomponents corresponding to the amplitude modulation frequencyassociated with control information. The filtered output from the BPF1182 is next supplied to a clock and data recovery circuit 1186, whichextracts the control information from the filtered output in a knownmanner and, in one example, supplies the control information or data tocontrol circuit 1161, as noted above. In one example, the controlcircuit may include a microprocessor circuit, for controlling oradjusting one or more parameters associated with the transmitter and/orreceiver portions of the secondary node transceiver based on messagesincluded in the control information or data. As used herein, the termmicroprocessor may include any computer or processor-based ormicroprocessor-based system including systems using microcontrollers,reduced instruction set computers (RISC), application specificintegrated circuits (ASICs), programmable gate array (PGA), fieldprogrammable gate array (FPGAs), logic circuits, and any other circuitor processor capable of executing the functions described herein.Microprocessor 1161 may be integrated with either DSP 1150 or DSP 902,or may be provided separate from each of these DSPs.

As noted above, both X and Y polarization components of each opticalsubcarrier are amplitude modulated. The circuitry shown in FIG. 9B isassociated with the X polarization component. It is understood thatsimilar circuitry is provided to extract control information from the Ypolarization component, for example, to improve accuracy of the detectedcontrol information.

Returning to FIG. 9A, the Rx DSP 1150 processes the digital samplessupplied thereto to provide user data streams D1 to D8, which were inputto the Tx DSP 902, as noted above in connection with FIGS. 4A and 5 .

III. First Data Path Implementation Example—Communication BetweenPrimary and Secondary Transceivers Based on Polarization Modulation

As discussed above, control information is communicated between thetransceivers in the primary (102)/secondary nodes (104) and line systemcomponents by way of amplitude modulation of the subcarriers.Communication between the primary node transceiver 106 and the secondarytransceiver 108 will next be described.

FIG. 10 shows an example of multiple subcarriers 300 (first opticalsignals, SC1 to SC8) and multiple communication signals 350 (secondoptical signals OOB-1 to OOB-8). Each of the subcarriers SC1 to SC8, asnoted above, are modulated to carry user data. Such modulation may beselected from the group including BPSK, QPSK, and m-amplitude quadraturemodulation (m-QAM), where m is a positive integer. Each of the opticalsignals OOB-1 to OOB-8 may carry transceiver-to-transceiver controlinformation and may be polarization modulated. Such polarizationmodulation may include polarization shift-keying (PolSK). Preferably,each of the optical signals OOB-1 to OOB-8 has a respective one of thefrequencies fO1 to fO8 that is spectrally adjacent a corresponding oneof the subcarrier frequencies f1 to f8, such that at least some of thefrequencies fO1 to fO8 are between an adjacent pair of subcarrierfrequencies (e.g., the frequency fO1 is between the frequencies f1 andf2, and the frequency fO5 is between the frequencies f5 and f6).However, in the example shown in FIG. 10 , the frequency fO8 is adjacentthe frequency f8, but is not between two adjacent subcarrierfrequencies.

In some implementations, both the subcarriers SC1 to SC8 and opticalsignals OOB1 to OOB8 may be generated in accordance with modulator drivesignal based electrical signals output from the DSP 902, for example.Thus, first control information associated with the above describedamplitude modulation may be transmitted in parallel or concurrently withsecond control information carried by the optical signals OOB-1 toOOB-8, as well as user data carried by subcarriers the SC1 to SC8.Moreover, one laser and modulator combination may be used to generateboth the subcarriers and optical signals OOB1 to OOB8. Additional lasersare not required to generate a control channel.

FIG. 11 depicts an example of an X polarization component and a Ypolarization component of OOB-1. In the example illustrated in FIG. 11 ,the OOB-1 may have either an X polarization 352 or a Y polarization 354depending on the data to be transmitted. For example, if a ‘1’ bit ofcontrol data is to be transmitted, the OOB signal 350 is output withlight primarily having the Y (e.g., transverse magnetic or TM)polarization or polarization state. On the other hand, if a ‘0’ bit ofcontrol data is to be transmitted, the OOB signal 350 is output withlight primarily having the X (e.g., transverse electric or TE)polarization or polarization state. Thus, control data may betransmitted by modulating the polarization of the OOB signal 350 toswitch or shift between first and second polarization states.

FIG. 12A illustrates in greater detail a transition from a ‘1’ bit, inwhich optical energy in optical signal OOB-1 is entirely (in thisexample) in one polarization state (“X-pol”) to a ‘0’ bit, in whichoptical energy is transferred to the other polarization state (“Y-pol”)at time t1. In FIGS. 12A and 12B, the amount of optical energy orintensity in the X polarization component of the signal OOB-1 isrepresented by an arrow OOB-1X, and the amount of optical energy orintensity in the Y polarization component of the signal OOB-1 isrepresented by an arrow OOB-1Y. As further shown in FIG. 12A, at timest2 to t4, the amount of optical energy in the X polarization componentof the signal OOB-1 decreases, while the amount of optical energy in theY polarization component of the signal OOB-1 increases. At time t5, theX polarization component of OOB-1 has little or no optical energy, andthe amount of optical energy in Y polarization component of OOB-1 is ata maximum, thereby indicating a ‘1’ bit.

FIG. 12B illustrates a transition from the ‘0’ bit back to the ‘1’ bit.Namely, as noted above, a maximum amount of optical energy is present inthe Y polarization at time t5. At times t6 to t8, however, the amount ofoptical energy in the Y polarization component of OOB-1 decreases, whilethe amount of optical energy in the X polarization component of OOB-1increases. At time t9, the optical energy in the X polarizationcomponent of OOB-1 is at a maximum, thereby corresponding to a ‘0’ bitof control data.

As seen in FIGS. 12A and 12B, at each time instant t1 to t9, the sum ofthe optical energy in the X (OOB-1X) and Y (OOB-1Y) polarizationcomponents of the signal OOB-1 remains constant, in this example. Thatis, the amplitude of the optical signal OOB-1 does not change.Accordingly, the signal OOB-1 does not interfere with or create noise inthe amplitude modulated signals described above that communicate controlinformation between the transceivers and the line system component(s).The signal OOB-1 may therefore be transmitted concurrently with suchamplitude modulated signals to provide an additional control channel,which, as noted above facilitates communication of control informationbetween the primary transceiver 106 and the secondary transceiver 108.

Although polarization modulation of the optical signal OOB-1 isdescribed above, it is understood that the remaining optical signalsOOB-2 to OOB-8 may similarly be polarization modulated to transmit ‘0’and ‘1’ bits in the same manner as that described above to providecommunication of control information to the secondary transceivers 108.

Transmission OOB signals will next be described in further detail withreference to FIG. 13 , which shows the Tx DSP block 903-2. As notedabove with respect to FIG. 4A, the Tx DSP block 902 includes the block903-1 and the block 903-2. The block 903-1 receives the data streams D-1to D-8, which are associated with a respective one of the subcarriersSC1 to SC8. The block 903-2, however, receives control data to betransmitted on one or more of the optical signals OOB-1 to OOB-8, forexample. The outputs of both blocks are fed to a further DSP block,block 903-3, which, based on the received inputs from the block 903-1and 903-2, provides digital signals. These digital signals, as notedabove, are converted to analog signals by the DACs 904, and then furtherprocessed by the driver circuits 906, which, in turn, provide drivesignals to the modulators 910. Based on such drive signals, themodulators 910 modulate light or an optical signal output from laser 908to provide a modulated optical signal including, in this example, thesubcarriers SC1 to SC8 carrying signal indicative of the user data andthe optical signals OOB-1 to OOB-8 carrying signal indicative of thecontrol information to be communicated between transceivers (e.g., thetransceiver 106 and the transceiver(s) 108).

The blocks 903-1 and 903-3 of the Tx DSP 902 are described above withreference to FIGS. 4 and 5 . The block 903-2 of the Tx DSP 902 will nextbe described with reference to FIG. 13 .

As shown in FIG. 13 , control data to be transmitted from the primarynode transceiver 106, for example, may be input to a mapper circuit1302, which maps the received bits to X and Y symbols to be carried bythe X and Y components, respectively, of the OOB signals. The mappercircuit 1302 has a first output that supplies symbols to be carried bythe X polarization component (X-pol symbols) to a first pulse shapefilter circuit 1304-1. The mapper circuit 1302 also has a second outputthat supplies symbols to be carried by the X polarization component(Y-pol symbols) to a second pulse shape filter circuit 1304-2. Bothfilter circuits 1304-1 and 1304-2 include, in one example, root raisedcosine filter circuitry. The outputs of the filter circuits 1304-1 and1304-2 are supplied to overlap and save (“OLS”) buffer circuits ormemories 1306-1 and 1306-2, respectively. The buffer circuits ormemories 1306-1 and 1306-2 provide outputs to corresponding Fast FourierTransform (FFT circuits) 1308-1 and 1308-2, which convert the buffercircuit outputs to frequency domain data. Such data is stored inmemories or bins, associated with the frequencies of the OOB signals.Each OOB signal has a relatively narrow bandwidth and carries controldata at a rate substantially less than the data rates associated withthe subcarriers SC1 to SC8. Accordingly, each OOB signal has a limitednumber of corresponding frequency bins. In the example shown in FIG. 13, in which the circuit block 903-2 provides signals for generating oneof the OOB signals, such as the signal OOB-1, two or four such bins arerequired to store the frequency domain data associated with the signalOOB-1.

The outputs of the FFT 1308-1 are provided to the IFFT 1010-1, and theoutputs of the FFT 1308-2 are provided to the IFFT 1010-2. Furtherprocessing by the IFFT 1010-1 and the IFFT-2, the lake last buffers ormemory circuits 1011-1 and 1011-2, the DACs 904, and the driver circuits906 is described above with respect to FIGS. 4 and 5 . Upon applicationof the drive signal outputs from the driver circuits 910, the opticalmodulators 910 outputs the optical subcarriers SC1 to SC8, as well asthe polarization modulated optical signals OOB-1 to OOB-8.

In particular, when a ‘1’, for example, is to be transmitted on thesignal OOB-1, the Y-polarization component has a maximum amount ofoptical energy, while the X polarization component has a minimal amountof optical energy, as noted above. To generate such X and Y components,drive signals are provided such that over frequencies associated withthe signal OOB-1, X polarized light is passed from laser 908 throughmodulators 910-3 and 910-4, polarization rotated to have a Ypolarization and then output through a polarization beam combiner (PBC)914. The modulators 910-1 and 910-2, however, substantially block suchlight at such frequencies, such that no light or little light having anX polarization is input to the PBC 914 for output onto the fiber 916.Accordingly, at the frequencies associated with the OOB-1, light havingthe Y polarization is output onto the fiber 916.

On the other hand, when a ‘0’, for example, is to be transmitted on thesignal OOB-1, the X-polarization component has a maximum amount ofoptical energy, while the Y polarization component has a minimal amountof optical energy, as further noted above. To generate such X and Ycomponents, drive signals are provided such that over frequenciesassociated with the signal OOB-1, X polarized light is passed from laser908 through the modulators 910-1 and 910-2 and then output through thepolarization beam combiner (PBC) 914. The modulators 910-3 and 910-4,however, substantially block such light at such frequencies, such thatno light or little light having an Y polarization is input to the PBC914 for output onto the fiber 916. Therefore, at the frequenciesassociated with the OOB-1, light having the Y polarization is outputonto the fiber 916.

As noted above with respect to FIG. 8 , OOB signals are received by areceiver along with the optical subcarriers and, therefore, are subjectto polarization demultiplexing, optical mixing, with local oscillatorlight, photoelectric conversion to analog electrical signals, processingby TIA/AGC circuits, and analog-to-digital conversion prior to input tothe Rx DSP 1150. As discussed in greater detail below, however, the RxDSP 1150 may have separate blocks for respectively outputting user dataassociated with the subcarriers SC1 to SC8 (block 1403 (FIG. 14 )) andcontrol data (block 1402 (FIG. 14 )).

As shown in FIG. 14 , the Rx DSP 1150 may include three blocks, two ofwhich are noted above as the blocks 1401 and 1402. The DSP block 1401includes circuitry that receives the outputs of the analog-to-digitalconversion circuits 1140-1 and 1140-2. As further shown in FIG. 14 , theDSP block 1401 supplies outputs which are processed by the block 1403 tothe output data streams D1 to D8. Other outputs are processed by theblock 1402 and output as transceiver-to-transceiver control data CDPS.

FIG. 15 shows the blocks 1401 and 1403 in greater detail. As notedabove, the analog-to-digital (A/D) circuits 1140-1 and 1140-2 outputdigital samples corresponding to the analog inputs supplied thereto. Inone example, the samples may be supplied by each A/D circuit at a rateof 64 G Sample/s. The digital samples correspond to symbols carried bythe X polarization the optical subcarriers and may be represented by thecomplex number XI+jXQ. The digital samples may be provided to a bufferor memory circuit, such as overlap and save buffers 1205-1 and 1205-2,as inputs to the Rx DSP block 1401. The FFT component or circuit 1210-1,also included in the block 1401, may receive the 2048 vector elements,for example, from the overlap and save buffer 1005-1 and convert thevector elements to the frequency domain using, for example, a fastFourier transform (FFT). The FFT component 1210-1 may convert the 2048vector elements to 2048 frequency components, each of which may bestored in a register or “bin” or other memory, as a result of carryouting the FFT.

The frequency components may then then be demultiplexed, and groups ofsuch components may be supplied to a respective one of chromaticdispersion equalizer circuits CDEQ 1212-1-0 to 1212-1-8 as inputs to theblock 1403. Each of the CDEQ circuits may include a finite impulseresponse (FIR) filter that corrects, offsets or reduces the effects of,or errors associated with chromatic dispersion of the transmittedoptical subcarriers. Each of the CDEQ circuits 1212-1-0 to 1212-1-8supplies an output to a corresponding polarization mode dispersion (PMD)equalizer circuit 1225-0 to 1225-8.

It is noted that digital samples output from the A/D circuits 1140-2associated with Y polarization components of subcarrier SC1 may beprocessed in a similar manner to that of digital samples output from theA/D circuits 1140-1 and associated with the X polarization component ofeach subcarrier. Namely, the overlap and save buffer 1205-2, the FFT1210-2 and the CDEQ circuits 1212-2-0 to 1212-2-8 may have a similarstructure and operate in a similar fashion as the buffer 1205-1, the FFT1210-1 and the CDEQ circuits 1212-1-0 to 1212-1-8, respectively. Forexample, each of the CDEQ circuits 1212-2-0 to 1212-8 may include an FIRfilter that corrects, offsets, or reduces the effects of, or errorsassociated with chromatic dispersion of the transmitted opticalsubcarriers. In addition, each of the CDEQ circuits 1212-2-0 to 1212-2-8provide an output to a corresponding one of the PMDEQ 1225-0 to 1225-8.

As further shown in FIG. 15 , the output of one of the CDEQ circuits,such as the CDEQ 1212-1-0 may be supplied to a clock phase detectorcircuit 1213 to determine a clock phase or clock timing associated withthe received subcarriers. Such phase or timing information or data maybe supplied to the ADCs 1140-1 and 1140-2 to adjust or control thetiming of the digital samples output from the ADCs 1140-1 and 1140-2.

Each of the PMDEQ circuits 1225 may include another FIR filter thatcorrects, offsets or reduces the effects of, or errors associated withPMD of the transmitted optical subcarriers. Each of the PMDEQ circuits1225 may supply a first output to a respective one of the IFFTcomponents or circuits 1230-0-1 to 1230-8-1 and a second output to arespective one of the IFFT components or circuits 1230-0-2 to 1230-8-2,each of which may convert a 256 element vector, in this example, back tothe time domain as 256 samples in accordance with, for example, aninverse fast Fourier transform (IFFT).

Time domain signals or data output from the IFFT 1230-0-1 to 1230-8-1are supplied to a corresponding one of the Xpol carrier phase correctioncircuits 1240-1-1 to 1240-8-1, which may apply carrier recoverytechniques to compensate for X polarization transmitter (e.g., the laser908) and receiver (e.g., the local oscillator laser 1110) linewidths. Insome implementations, each carrier phase correction circuit 1240-1-1 to1240-8-1 may compensate or correct for frequency and/or phasedifferences between the X polarization of the transmit signal and the Xpolarization of light from the local oscillator 1110 based on an outputof the Xpol carrier recovery circuit 1240-0-1, which performs carrierrecovery in connection with one of the subcarrier based on the outputsof the IFFT 1230-01. After such X polarization carrier phase correction,the data associated with the X polarization component may be representedas symbols having the complex representation xi+j*xq in a constellation,such as a QPSK constellation or a constellation associated with anothermodulation formation, such as an m-quadrature amplitude modulation(QAM), m being an integer. In some implementations, the taps of the FIRfilter included in one or more of the PMDEQ circuits 1225 may be updatedbased on the output of at least one of the carrier phase correctioncircuits 1240-0-1 to 1240-8-01.

In a similar manner, time domain signals or data output from the IFFT1230-0-2 to 1230-8-2 are supplied to a corresponding one of the Ypolcarrier phase correction circuits 1240-0-2 to 1240-8-2, which maycompensate or correct for the Y polarization transmitter (e.g., thelaser 908) and receiver (e.g., the local oscillator laser 1110)linewidths. In some implementations, each carrier phase correctioncircuit 1240-0-2 to 1240-8-2 may also corrector or compensate or correctfor frequency and/or phase differences between the Y polarization of thetransmit signal and the Y polarization of light from the localoscillator laser 1110. After such Y polarization carrier phasecorrection, the data associated with the Y polarization component may berepresented as symbols having the complex representation yi+j*yq in aconstellation, such as a QPSK constellation or a constellationassociated with another modulation formation, such as an m-quadratureamplitude modulation (QAM), m being an integer. In some implementations,the output of one of the circuits 1240-0-2 to 1240-8-2 may be used toupdate the taps of the FIR filter included in one or more of the PMDEQcircuits 1225 instead of or in addition to the output of at least one ofthe carrier recovery circuits 1240-0-1 to 1240-8-1.

As further shown in FIG. 15 , the output of carrier recovery circuits(e.g., the carrier recovery circuit 1240-0-1), may also be supplied tothe carrier phase correction circuits 1240-1-1 to 1240-8-1 and 1240-0-2to 1240-8-2 whereby the phase correction circuits may determine orcalculate a corrected carrier phase associated with each of the receivedsubcarriers based on one of the recovered carriers, instead of providingmultiple carrier recovery circuits, each of which being associated witha corresponding subcarrier.

Each of the symbols to bits circuits or components 1245-0-1 to 1245-8-1may receive the symbols output from a corresponding one of the circuits1240-0-1 to 1240-8-1 and map the symbols back to bits. For example, eachof the symbol to bits components 1245-0-1 to 1245-8-1 may map one Xpolarization symbol, in a QPSK or m-QAM constellation, to Z bits, whereZ is an integer. For dual-polarization QPSK modulated subcarriers, Z isfour. Bits output from each of the components 1245-0-1 to 1245-8-1 areprovided to a corresponding one of the FEC decoder circuits 1260-0 to1260-8.

Y polarization symbols are output form a respective one of the circuits1240-0-2 to 1240-8-2, each of which having the complex representationyi+j*yq associated with data carried by the Y polarization component.Each Y polarization, like the X polarization symbols noted above, may beprovided to symbols to a corresponding one of the bit to symbol circuitsor components 1245-0-2 to 1245-8-2, each of which having a similarstructure and operating a similar manner as the symbols to bitscomponent 1245-0-1 to 1245-8-1. Each of the circuits 1245-0-2 to1245-8-2 may provide an output to a corresponding one of the FEC decodercircuits 1260-0 to 1260-8.

Each of the FEC decoder circuits 1260 may remove errors in the outputsof the symbol to bit circuits 1245 using forward error correction. Sucherror corrected bits, which may include user data for output to oroutput from the secondary node 108, may be supplied as a correspondingone of the outputs D1 to D8 from block 1403.

It is noted that, in the above example, eight overlap and save buffers,FFTs, replicators, pulse shape filters with the X and Y polarizations,respectively, in the Tx DSP corresponding in number to the number ofoptical subcarriers that may be generated, i.e., eight. Likewise eightCDEQs IFFTs, carrier phase correction circuits, symbol to bits circuitsand FEC encoders are provided for each polarization in the Rx DSPcorresponding to the eight subcarriers. If more subcarriers are to begenerated, such as 16, than a corresponding number of such componentsare preferably provided in the Tx and Rx DSPs.

FIG. 16 shows the Rx DSP block with an emphasis on the details of theblock 1402. As noted above, the block 1402 receives outputs from theblock 1401, and, based on such outputs, supplies control data carried byan OOB signal, such as the signal OOB-1. The block 1402 includesfrequency bins or memories 1602 which receives outputs from the FFT1210-1 and 1210-2. Such outputs are frequency domain data correspondingassociated with data carried by the signal OOB-1, for example. Turningto FIG. 17 , such frequency bins that are associated with the signalOOB-1. More specifically, each of the respective frequency bins 1602 cancorrespond to particular frequencies associated with OOB-1. Such binsstore frequency domain data associated with OOB-1. Since the signalOOB-1, for example, has a relatively narrow bandwidth, not all of thebins 1602 will store data. Accordingly, the circuitry 1604 detects apeak frequency bin and outputs the data stored in the bin, as well Mbins adjacent to it (M may be an integer, such as 2 or 4). For example,as shown in FIG. 17 , the bin 1702 is the peak frequency bin, and theM=2 bins adjacent to the bin 1702 are the bins 1704, 1706, 1708, and1710. The outputs of these bins are provided to an inverse Fast FourierTransform (IFFT) circuits 1606-1 (associated with the X component of thesignal OOB-1) and 1606-2 (associated with the Y component of the signalOOB-1). The IFFT circuits 1606 supply time domain data to buffers, suchas the overlap and save buffer circuits 1608-1 and 1608-2, and thebuffered time domain data is supplied to a filter, including, forexample, a multiple-input-multiple-output (MIMO) filter 1610 having alimited number of taps. The filter 1610 is provided to correct fordistortions in the data output from the buffer circuits 1608-1 and1608-2 that may be attributable to a rotation of the X and Ypolarization components of the signal OOB-1, for example, duringpropagation along an optical fiber link.

As further shown in FIG. 16 , the filter 1610 provides an output to adecision circuit that outputs either ‘0’ or ‘1’ bits based on suchoutput. These bits constitute control data (CDPS in FIG. 13 ) outputfrom the hub or the primary transceiver 106, for example. Similarcircuitry may be provided in the receiver portion of the transceiver 106to detect and output control data output from one or more of thesecondary transceivers 108.

While FIGS. 15-17 show the Rx DSP 1150 as including a particularquantity and arrangement of functional components, in someimplementations, the DSP 1150 may include additional functionalcomponents, fewer functional components, different functionalcomponents, or differently arranged functional components.

IV. Second Data Path Implementation Example—Communication BetweenPrimary and Secondary Transceivers Based on Amplitude Modulation at aPlurality of Frequencies

In the above First Data Path Implementation Example, the opticalsubcarriers output from a transceiver, such as the primary transceiver106, are subject to amplitude modulation to carry control informationassociated with a first data path (e.g., data path CC1 in FIG. 2A).Further, as noted above, polarization modulation may be employed on aspectrally narrow optical signal to carry addition control informationassociated with a second data path (e.g., data path CC3 in FIG. 2A). Insome implementations, amplitude modulation may be employed to carrycontrol information associated with different data paths. For example,as described in greater detail below, the optical subcarrier shown inFIG. 3 may be subject to a first, second, and third amplitudemodulations in both the downstream and upstream directions. Each suchamplitude modulation may be at a different frequency and may beassociated with different control information, as well as a differentdata path. In one example, the modulation frequencies are between 1 MHzand 2 MHz (band A), 3 MHz and 4 MHz (band B), and 6 MHz and 7 MHz (bandC), although other bands or ranges may be employed. Accordingly, theamplitude modulation is at frequencies less than that associated withthe transmitted user data, which is approximately in a range of 10 GHzto 100 GHz.

FIG. 18 shows the optical system 100 of FIG. 1A further labeled witharrows indicating the direction and amplitude modulation employed toexchange control information between transceivers, optical gateways, andcentral software to thereby realize alternative data pathimplementations to those described above with references to FIGS. 1-17 .As shown in FIG. 18 , the arrow 1802 indicates that the opticalsubcarriers, such as the SC1 to SC8, output from a transmitter in theprimary transceiver 106 may be amplitude modulated at a first frequencyor frequencies in band B, for example, to carry control information tothe OGW 103-1 and for further transmission to the central software 111,as noted above. The optical subcarriers may be further amplitudemodulated in the transmitter of the primary transceiver 106 at afrequency or frequencies in band C, for example, to provide controlinformation to one or more secondary transceivers 108 through the OGW103-1, the sub-system 105, and the OGW 103-2 (indicated by the arrow1812). In addition, the OGW 103-2 may also amplitude modulate theoptical subcarriers passing therethrough at a frequency in band A toprovide control information, such as from the central software 111, asfurther noted above, to one or more of the secondary transceivers 108(indicated by the arrow 1810).

As further shown in FIG. 18 , the arrow 1808 indicates that one or moreof the optical subcarriers SC1 to SC8 output from a transmitter in oneof the secondary transceivers 108, for example, may be amplitudemodulated at a frequency or frequencies in band B, for example, to carrycontrol information to the OGW 103-2 and for further transmission to thecentral software 111, as noted above. The optical subcarriers may befurther amplitude modulated in the transmitter of one of the secondarytransceivers 108 at a frequency or frequencies in band C, for example,to provide control information to the primary transceiver 106 throughthe OGW 103-2, the sub-system 105, and the OGW 103-1 (indicated by thearrow 1806). Such amplitude modulation transmission is shared, in oneexample, among each transceiver 108. In that case, more than one of thesecondary transceivers 108 may transmit control information at afrequency in band C at the same time. Accordingly, control informationtransmission from the secondary transceivers 108 to the primarytransceiver 106 may be carried out in bursts of relatively shortduration to reduce the likelihood that control information output fromone of the secondary transceivers 108 will interfere or collide with thecontrol information output from another second transceiver. Due to thispossibility of collisions, in some implementations, the secondarytransceivers can assume the control information was not received by theprimary transceiver and can retransmit the control information (e.g., ata random or pseudo random interval) until the primary transceiver 106sends an acknowledgement message to the secondary transceiver 108 thatsent the control information that such information was successfullyreceived. In some implementations, one or more “back off” algorithms canbe used to ensure secondary transceivers that are independentlycontrolled will successfully send control information to the primarytransceiver. One such example is the pseudo-random exponential back offalgorithm.

In addition, the OGW 103-1 may also amplitude modulate the opticalsubcarriers passing therethrough at a frequency in band A to furtherprovide control information, such as from central software 111, asfurther noted above, to the primary transceiver 106 (indicated by thearrow 1804).

Generation of multiple amplitude modulated data paths will next bedescribed. As noted above, the optical subcarriers can be amplitudemodulated, collectively, to carry control information associated with aparticular data path (see FIG. 3 ). FIG. 19 shows example circuitry 1992that may be included in the AM signal generator 992 described above withrespect to FIG. 4A instead of the circuitry 992-1. Here, the AM signalgenerator 992 is modified to include the circuitry 1992 to amplitudemodulate the subcarriers at different frequencies to carry first andsecond control information, instead of amplitude modulation at onefrequency, as noted above with respect to FIG. 4B. As in the examplenoted above, the AM signal generator 992 provides each of the outputsAMO-1 to AMO-4 to a respective input of the DACs 904-1 to 904-4 (seeFIG. 4A). These signals are generated in such a way that the DACs 904output analog signals that include multiple amplitude modulated signalsoverlaying or superimposed on the data carrying DAC outputs. Based onsuch DAC outputs, the Mach-Zehnder modulator driver circuits (MZMDs)906, in turn, output drive signal to the MZMs 910, as noted above.Accordingly, the combined MZM outputs supply optical subcarrierssuperimposed with multiple amplitude modulated signals at differentfrequencies based on the outputs of the signal generator 992, wherebyboth the X and Y polarization components of each optical subcarrier aresubject to such amplitude modulation.

Returning to FIG. 19 , the circuitry 1992 includes a multiplier circuit1902-1 that multiplies first control information CD1 by a cosinefunction, cos(ω_(B)t), where ω_(B) is indicative of a frequency of theamplitude modulation and t is time. For example, ω_(B) may correspond toan amplitude modulation frequency within band B for transmission ofcontrol information to the OGW 103-1 and further transmission to thecentral software 111 (see arrow 1802 in FIG. 18 ). In a similar manneras that described above in regard to FIG. 4B, the output of themultiplier 1902-1 is provided to the adder 1903-1 which adds 1 toproduct supplied by the multiplier 1902-1 to ensure that a positivenumber is obtained. As further shown in FIG. 19 , the resulting sumoutput from the adder 1903-1 is provided to a multiplier 1904-2, whichmultiplies such sum by a carrier frequency ω_(Carrier).

The circuitry 1992 also includes, for example, a multiplier circuit1902-2 that multiplies control information CD2 by a cosine function,cos(ω_(C)t), where ω_(C) is indicative of a frequency of anotheramplitude modulation and t is time. For example, ω_(C) may correspond toa frequency within band C for transmission of control information to thetransceivers 108 via the OGW 103-1, the sub-system 105, and the OGW103-2 (the arrow 1812 in FIG. 18 ). The adder 1903-2 and the multiplier1904-2 operate in a similar manner as the adder 1903-1 and themultiplier 1904-1 (except that the multiplier 1904-1 multiplies theoutput of the adder 1903-2 by cos(ω′_(carrier)t)). As further shown inFIG. 12 , the outputs of the multiplier circuits 1904-1 and 1904-2 areprovided to an adder circuit 1906, which adds such outputs and theresulting sum (AMO-1 in FIG. 4A) is combined with a corresponding outputfrom the DSP 902 and input to the DAC 904-1. Accordingly, amplitudemodulation at different frequencies, a first amplitude modulation inband B and a second amplitude modulation in band C, are fed to the DAC904-1. As a result, both X and Y polarization components of each opticalsubcarrier are amplitude modulated at multiple frequencies to carrymultiple control information streams.

It is understood that additional circuitry similar to that shown in FIG.19 is also included in the AM signal generator 992, in this example, toprovide similar signals (AMO-2 to AMO-4) to the inputs of remaining theDACs 904-2 to 904-4. As noted above, based on such inputs, the combinedoutput of the MZMs 910 supplies optical subcarriers that arecollectively amplitude modulated, such that both the first and secondamplitude modulation signals are superimposed onto the opticalsubcarriers to thereby carry first and second control informationintended for the OGW 103-1 and a secondary transceiver 108,respectively, for example.

The OGW-1 and the OGW-2 in FIG. 19 generate and amplitude modulatedsubcarriers in a manner similar to that described in connection withFIG. 7 . As noted with respect to FIG. 18 , the OGW-1 may provideamplitude modulated optical subcarriers supplied to the primarytransceiver 106 at a frequency within band A (see arrow 1804), and theOGW-2 may modulate the optical subcarriers supplied to one or more ofthe transceivers 108 also in band A (see arrow 1810).

Moreover, one or more of the secondary transceivers 108 may includetransmitter circuitry, similar to the circuitry 1992, to amplitudemodulate subcarrier(s) output therefrom with multiple amplitudemodulation frequencies (see arrows 1806 and 1808), each corresponding toa respective control data stream or data path.

Detection of control information carried by amplitude modulatedsubcarriers at a receiver, such as a module 1155, in the primary node106 will next be described with reference to FIGS. 8, 9A and 20 . Asnoted above, with respect to FIGS. 8 and 9A, control information or datamay be determined based on outputs from either the TIA/AGCs circuits1134 (FIG. 8 ) or the mean square detector 1160 (FIG. 9A), each of whichsupplies electrical signals based on electrical signals output from thephotodiode circuitry 1130. FIG. 9B shows additional circuitry forfiltering the outputs of either of the circuits 1134 or 1160 in order tooutput control information associated with one control informationstream. FIG. 20 shows circuitry 2002 that may replace the circuitryshown in FIG. 9B to provide first (CD1) and second (CD2) controlinformation or control information streams associated with first andsecond amplitude modulations, respectively, of the optical subcarriers.

As shown in FIG. 20 , the outputs of either the TIA/AGC 1134 or the meansquare detector 1160 may be provided to the first and the secondbandpass filters 1182 and 1183. The first bandpass filter 1182 passessignals associated with a first amplitude modulation having a frequencyor frequencies, for example, in band C associated with thetransceiver-to-transceiver data paths (see arrows 1806 and 1812 in FIG.18 ). Moreover, the second bandpass filter 1183 passes signalsassociated with a second amplitude modulation having a frequency orfrequencies, for example, in band A associated with the OGW (eitherOGW-1 or OGW-2) to transceiver data paths. The output of the bandpassfilter 1182 is supplied to clock and data recovery circuit 1186 tothereby supply first control information CD1 associated with the firstamplitude modulation of the subcarriers, and the output of bandpassfilter 1183 is supplied to the clock and data recovery 1187 to therebyprovide second control information CD2 associated with the secondamplitude modulation of the subcarriers.

The circuitry 2002 is provided to detect and output control informationassociated with the X polarization component of the optical subcarriers.As noted above, however, each optical subcarrier also has a Ypolarization component, which is also amplitude modulated. It isunderstood, that circuitry similar to the circuitry 2002 is provided,for example, to output control information associated with the amplitudemodulation of the Y polarization component of each optical subcarrier.In a further example, control information or data CD1 and CD2 may beprovided to control circuit 1161, such that such control information maybe used to control or adjust a parameter or function of either theprimary or secondary transceivers. In a further example, one or both ofthe CD1 and CD2 may include information indicative of a number ofsubcarriers to be output from a transceiver, as noted above. As furthernoted above, such information may be used by control circuit 1161 toadjust the number of optical subcarriers, by either adding or reducing,the number of optical subcarriers that are output from the transceiver.

An example implementation of the data path connections, CC3, CC4, CC1,CC5, and CC2 that facilitate control channel communication between thesecondary transceiver 108-n and the network management system 109 (andthe central software 111) will next be described. As noted above, thesecondary transceivers 108, such as the transceiver 108-n output opticalsubcarriers carrying data, such as one or more of the opticalsubcarriers SC1 to SC8, and such subcarriers may be amplitude modulatedat a first frequency, such as a frequency in band C, to carry firstcontrol information. In addition, the subcarriers may be furtheramplitude modulated at a second frequency, such as a frequency in bandB, to carry second control information. Such amplitude modulated opticalsignals are generated by circuitry similar to that shown in FIGS. 4A and20 , for example. These signals are transmitted as part of the upstreamsignal US along an optical communication path including the OGW 103-2,the subsystem 105, and the OGW-1, the optical fiber 115-2, to areceiver, such as the module 1155 shown in FIG. 8 , provided in theprimary transceiver 106, thereby implementing the data path CC3. At theOGW 103-2, the second control information may be detected and suppliedto the central software 111 and the network management system 109, asdescribed above with reference to FIG. 7 . For example, a tapped portionof the incoming optical signal to the OGW 103-2 is detected by aphotodiode, similar to the photodiode 711, and the resulting electricalsignal is processed by circuitry in a microprocessor or microcontroller,similar to that shown in FIG. 7 , to output the second control data tothe central software 111 in the network management system 109.

As noted above with respect to FIGS. 8, 9A and 20 , the TIA/AGCs 1134 orthe mean square detector 1160 may output signals indicative of the firstcontrol information to the bandpass filters 1182 and 1183. The bandpassfilter 1182, however, passes signals associated frequencies in band C.Such signals are associated with the first control data. Upon processingof the output of the bandpass filter 1182 by the clock and data recoverycircuit 1186 (see FIG. 20 ), the first control data is output. Suchcontrol information, in one example, may be provided to the DSP 902 orcontrol circuitry in the receiver or transmitter portions of the primarytransceiver 106 to report status of the secondary transceiver 108-n orto adjust a parameter, parameter associated one or more of the opticalsubcarriers SC1 to SC8 output from the transceiver 106.

Alternatively, control information CD1 may be input to the AM signalgenerator 992, to amplitude modulate the optical subcarriers in a mannersimilar to that described with reference to FIGS. 4A, 4B, and 20 , tothereby implement the data path CC4. For example, the optical subcarriermay be amplitude modulated at a frequency in band B to thereby carry thecontrol information CD1, which originated from the transceiver 108-n.The optical subcarriers are transmitted on another optical communicationpath, including the fiber 115-1, to the OGW 103-1 (data path CC1). Againreferring to FIG. 7 , a portion of the amplitude modulated opticalsubcarriers is output from a tap, such as the tap 711, converted to anelectrical signal, which is then processed by a microprocessor ormicrocontroller (data path CC5) to provide the control information(originating from the secondary node 108-n) to the network managementsystem 109 and the central software 111 (data path CC2).

Thus, in the above example, control information is provided, along withuser data carried by the optical subcarriers, without additional opticalor electrical components, from a transceiver to the central software ina manner that bypasses the node equipment housing such transceiver.Moreover, by amplitude modulating the optical subcarriers to carry thecontrol information, more capacity is made available for transmission ofuser data. In addition, although the above example employed amplitudemodulation to carry the control information from the secondarytransceiver 108-n to the primary transceiver 106, polarizationmodulation, such as polarization shift keying, as described above, maybe employed to carry such control information, to implement data pathCC3.

Similar data paths may be employed in the opposite direction as thatdescribed above to transmit control information from the centralsoftware 111 to the transceiver. Alternatively, as described previously,control information may be provided to/from the central software via anoptical gateway (OGW) nearest the transceiver intended for such controlinformation.

It is noted that amplitude modulation at frequencies associated withcontrol information intended for the central software 111 may propagatefrom, for example, the primary transceiver 106 to one or more of thesecondary transceivers 108. Since such control information is notintended for receipt at the secondary transceivers 108, the bandpassfilters 1182 and 1183, for example, are configured to block or filterout frequencies associated with that control information. Accordingly,in the above example, control information for output to the centralsoftware 111 is associated with amplitude modulation frequencies band B.Since, each OGW includes a tap to detect such amplitude modulation (seeFIG. 7 ), such amplitude modulation is blocked by the OGWs 103-1 and103-2 and is transmitted with the subcarriers to the secondarytransceivers 108. Accordingly, as noted above, bandpass filters 1182 and1183 pass signals with frequencies associated with control informationto be received by the secondary transceivers 108, namely, in the aboveexample, frequencies in bands A and C, such that signals associated withband B are blocked or not processed in the transceivers 108. As notedabove, such information may be used by control circuit 1161 provided inthe transceivers, to control or adjust a parameter or function of thetransceivers, such as the number of optical subcarriers to be outputfrom the transceiver.

III. Example Techniques for Configuring Transceivers with Respect to anOptical Communications Network

As described herein, in some implementations, two or more transceiverscan exchange information with one another directly to configurethemselves for use on an optical communications network by oftransmission of amplitude modulated (AM) signals and the informationassociated with such signal may be used by circuitry in thetransceivers, such as control circuit 1161 to adjust or control aparameter or functionality of the transceiver. As an example,transceivers can communicate with one another to establish control pathsand/or communication path between them, and reconfigure the controlpaths and/or communication paths dynamically (e.g., to correct formisconfigurations with respect to the network, to optimize theperformance of the transceivers, etc.). In some implementations, thisprocess can be performed by the transceivers, independent from thecentral software, the host equipment, and/or the node equipment.

As an example, FIG. 21 shows a process 2100 for configuring transceiversfor use on an optical communications network. The process 2100 can beperformed by a hub transceiver 2102 and one or more edge transceivers2102 a-2102 n. In some implementations, the hub transceiver 2102 can besimilar to the primary transceivers 106 described herein (e.g., withrespect to FIGS. 1, 2A-2C, and 18 ). In some implementations, each ofthe edge transceivers 2102 a-2102 n can be similar to the secondarytransceivers 108 described herein (e.g., with respect to FIGS. 1, 2A-2C,and 18).

In some implementations, at least some of the transceivers can beinitially identical to one another (e.g., initially identical inconfiguration). In some implementations, these transceivers can bere-configured to function as a hub transceiver or an edge transceiver asa part of a configuration process (e.g., once the transceivers haveestablished communications with one another). An example configurationprocess is shown in FIG. 29 .

According to the process 2100, each of the hub transceiver 2102 and theedge transceivers 2102 a-2102 n are initiated for operation (block2106).

As an example, the hub transceiver 2102 can power up one or more of itscomponents (e.g., one or more of the components described with respectto FIGS. 4A, 4B, 5, and 6 ). Further, the hub transceiver 2102 candetermine which optical spectrum has been assigned to it for creationand distribution of optical subcarriers among edge transceivers forcommunication over the optical communications network, and “power up”each of those optical subcarriers In some implementations, an “idle”optical subcarrier may be transmitted that carries informationindicative of a blank data frame, which can be a data frame thatincludes a pre-defined pattern of data, such as all zeros, all ones, orsome other pattern of bits. In some implementations, the idle subcarriercan carry information indicative of a random or pseudo-random data(e.g., a pseudo random bit sequence, PRBS).

FIG. 33 shows an example of circuitry 3300, which may be employed togenerate an optical subcarrier, here, SC1, carrying data associated witha PRBS or blank packets, such that optical subcarrier SC1 is an idlesubcarrier. Circuitry 3300 includes generator circuit 3301, whichgenerates PRBS or blank frames as an output. Circuitry 3300 alsoincludes a switch 3302 that is coupled to receive the output of circuit3301 as well as user data stream D1. In a first mode, switch 3302supplies user data stream D1 to FEC encoder circuit 1002-1, which inturn supplies an encoded output that is further processed, as describedin connection with FIGS. 4A and 5 , to provide optical subcarrier SC1.

Switch 3302, under control of control circuit 1161, for example, may beconfigured in a second mode, in which switch 3302 supplies the PRBS orblank data frames to FEC encoder circuit 1002-1 instead of user datastream D1. In that case, the PRBS or blank data frames are processed, asdescribed in connection with FIGS. 4A and 5 , to provide opticalsubcarrier SC1 carrying information indicative of such PRBS or blankdata frames, such that optical subcarrier SC1 may be considered an idlesubcarrier.

Examples of optical subcarriers are described, for example, with respectto FIGS. 3 and 10 . In some implementations, data regarding the hubtransceiver's assigned optical subcarriers can be stored in a storagedevice of the hub transceiver and/or in a firmware of the hubtransceiver. In some implementations, data regarding the hubtransceiver's assigned optical subcarriers can be transmitted to the hubtransceiver from an external source (e.g., the central software 111).

In some implementations, the hub transceiver 2102 can also determine theallocation of data capacity or bandwidth associated with opticalsubcarriers to one or more of the edge transceivers for use on theoptical communications network. In some implementations, data regardingthese allotments also can be stored in a storage device of the hubtransceiver and/or in a firmware of the hub transceiver.

Further, the edge transceivers 2102 a-2102 n also can power up one ormore of their components (e.g., one or more of the components describedwith respect to FIGS. 8, 9A, and 9B). Further, the edge transceivers2102 a-2102 n can monitor the optical communications network for thepresence of the hub transceiver 2102. For instance, the edgetransceivers 2104 a-2104 n can “scan” or search the optical signalsoutput from one or more hub transceivers prior to establishingcommunication with such hub transceiver(s). Such scanning is describedin greater detail below.

After initialization, the hub transceiver 2102 broadcasts a beaconmessage to each of the edge transceivers 2104 a-2104 n (block 2108) byway of, for example, one or more of the AM signals noted above. Thebeacon message includes information that enables each of the edgetransceivers to request an allotment of bandwidth associated with one ormore optical subcarriers for use on the optical communications network.For example, the beacon message can include the identity of the hubtransceiver 2102 (e.g., a unique identifier that differentiates the hubtransceiver from other hub transceivers on the optical communicationsnetwork). As another example, the beacon message can include a list ofbandwidths of each of the optical subcarriers that have been assigned tothe hub transceiver 2102 for allotment, the properties of each of theoptical subcarriers (e.g., the frequencies and bandwidths associatedwith each optical subcarrier), and the status of each of the opticalsubcarriers (e.g., whether it has already been allotted to an edgetransceiver, or whether it available for allotment to an edgetransceiver). As another example, the beacon message can include anindication of the number of edge transceivers that are currentlyconnected to hub transceiver 2102 and/or an identifier of each of thoseedge transceivers (e.g., a unique identifier that differentiates theedge transceiver from other edge transceivers on the opticalcommunications network). As another example, the beacon message caninclude an indication the properties of the hub transceiver 2102 (e.g.,the type of modulation used by the hub transceiver 2102 in communicatingwith other types, the type of error correction used by the hubtransceiver 2102, or any other information regarding the hub transceiver2102 and its operations). As another example, the beacon message caninclude instructions for requesting an allotment of one or more opticalsubcarriers (e.g., an indication of a procedure that is to be followedby the edge transceiver to request an allotment of one or more opticalsubcarrier from the hub transceiver, the number of idle opticalsubcarriers that are required to enable certain line systems andcommunications protocols, etc.). The information associated with thebeacon message may be carried by an AM signal noted above and receivedby control circuit 1161 present in each of the hub and/or leaf nodes foradjusting the functionality or configuration of one or more componentsor circuits shown in FIGS. 4A, 4B, 5, 6A, 8, and 9A-9C in the hub and/orleaf nodes.

In some implementations, the beacon message can be broadcast to multipleones of the edge transceivers 2104 a-2104 n (or to all the edgetransceivers 2104 a-2104 n) concurrently. For example, the beaconmessage can be broadcast to each of the edge transceivers 2104 a-2104 nusing a common OOB baseband carrier, such as the AM signals noted above,whereby each of the edge transceivers 2104 a-2104 n receives arespective copy of the beacon message concurrently (or substantiallyconcurrently). Further, the beacon message can be broadcast repeatedlyover a period of time (e.g., periodically or intermittently).

After receiving the beacon message from the hub transceiver 2102, eachof the edge transceivers 2104 a-2104 n can transmit a message to the hubtransceiver 2102 requesting allotment of bandwidth associated with theoptical subcarriers (block 2110). The bandwidth allotment request may bea request for to assign an optical subcarrier to the edge transceiver.Alternatively, the allotment request may be a request for a certainamount of capacity, which may be distributed over multiple subcarriersor may be associated with one subcarrier. For example, the bandwidthallotment request may be a request for data capacity associated with aspecific subcarrier. Such a request may include a reference to or anidentification of a specific optical subcarrier. In another example, thebandwidth allotment or allocation request may be a request for capacitywithout reference to a particular subcarrier. In that case, the hubtransceiver may assign bandwidth associated with one subcarrier or mayassign bandwidth shared by multiple subcarriers. That is, in oneexample, if each subcarrier has an associated bandwidth or capacity of100 Gbit/s, and the edge transceiver requests 100 Gbit/s, the hub mayassign one subcarrier to the edge transceiver, or assign 50 Gbit/s fromtwo subcarriers to the edge transceiver.

In the example shown in FIG. 21 , control circuit 1161 in a first edgetransceiver 2104 a can determine, based on the beacon message, that oneor more particular optical subcarriers or a certain amount of bandwidthor capacity are available for use on the optical communications network.In turn, the edge transceiver 2104 a can generate a request message inaccordance with the instructions provided in the beacon message, andinclude in the request message an indication of the available bandwidthor one or more requested optical subcarriers (e.g., a list of theidentifiers of the requested optical subcarriers or bandwidth, such asan index value). In one example, the request message may be output bycontrol circuit 1161 as signal supplied to a VOA, such as VOA 915 inFIG. 4A, to amplitude modulate (AM) the optical subcarriers supplied bythe leaf node transmitter. Alternatively, the message may be output asdata CD1, which is subject to further processing as discussed above inFIG. 4B to output the AM signal. In a further example, the message mayoutput by control circuit 1161 as a plurality of gain values G1 to G8 togenerate the AM signal, as noted above with respect to FIG. 6A. It isunderstood that, in one example, the transmission and receipt of allmessages described herein between the hub and edge nodes may be carriedout using the AM signal generation and detection techniques describedherein.

In some implementations, each of the edge transceivers 2104 a-2104 n cantransmit respective request messages in a manner similar to thatdescribed above to the hub transceiver 2102 over a common communicationschannel (e.g., a “party line”). For example, each of the edgetransceivers 2104 a-2104 n can repeatedly transmit the respectiverequest messages periodically or intermittently, such as according to arandom or pseudo random interval) until the edge transceiver receivesthe message acknowledging the request, or until a certain “time-out”interval has expired. Accordingly, the hub transceiver 2102 may receivemultiple request messages from multiple edge transceivers using thecommon communications channel, such as a common AM frequency, over time.

Upon receiving a request message, a control circuit 1161 in the hubtransceiver 2102 detects the information contained in the message in amanner similar to that described. Based on the received information,control circuit 1161 in the hub generates a message that is carried by afurther AM signal generated in a manner described above (see, forexample, FIGS. 4A, 4B, and 6A). The further AM signal is transmitted tothe edge transceiver 2104 a acknowledging the request (block 2112). Insome implementations, the edge transceiver 2104 a can repeatedlytransmit the message requesting allotment of bandwidth (e.g., repeatstep 2110 periodically or intermittently, such as according to a randomor pseudo random interval) until the edge transceiver receives themessage acknowledging the request, or until a certain “time-out”interval has expired.

Further, upon receiving the request message, the hub transceiver 2102processes the request in a manner similar to that described above (block2114). As an example, the hub transceiver 2102 can determine whether therequest can be fulfilled (e.g., whether the requested bandwidth isavailable or one or more optical subcarriers are still available forallotment to an edge, or whether the one or more digital subcarriershave already been allotted). If so, the hub transceiver 2102 can fulfillthe request (e.g., by assigning the one or more requested opticalsubcarrier or the requested bandwidth to the edge transceiver 2104 athat had made the request, and monitoring those optical subcarrier(s)for transmission from the edge transceiver). Further, the hubtransceiver can record the subcarrier assignment and/or bandwidthallotment (e.g., in a storage device or in its firmware). However, ifthe request cannot be fulfilled, the hub transceiver 2102 can determine,in some instances, one or more modifications to the request that wouldenable the request to be fulfilled (e.g., identifying additionalbandwidth or optical subcarriers that are available to be assigned tothe edge transceiver).

In some implementations, processing the request can also includeauthenticating an identifier of the edge transceiver 2104 a (e.g., anInitial Device Identifier, IDevID), verifying the role associated to theedge transceiver 2104 a with respect to the optical communicationsnetwork (e.g., the role of an “edge” transceiver), modifying the roleassigned to the edge transceiver 2104 a, verifying that the edgetransceiver 2104 a can perform particular operations with respect to theoptical wireless network, verifying licenses associated with the edgetransceiver 2104 a, updating the licenses associated with the edgetransceiver 2104 a, and/or any other function. In one example, controlcircuit 1161 may be configured to carry out each of the foregoing basedon information contained in the received message.

In some implementations, one or more of the edge transceivers can beassociated with a license that regulates the use of those edgetransceivers. For example, a first entity (e.g., a vendor of the edgetransceivers) may grant a license to a second entity (e.g., a user ofthe edge transceivers) that authorizes the edge transceiver to operateaccording to a particular set of capabilities (e.g., a particularbandwidth or throughput) and/or perform a particular set of operations(e.g., one or more of the operations described herein). Data regardingthis license can be stored on the edge transceivers, and modified if anychanges to the license are made (e.g., as a part of the process 2100).The edge transceivers can operate in accordance with the license data.

In some implementations, a license may authorize the use of one or moreparticular transceivers. For example, if a user wishes to deploy 100transceivers, he may obtain a license authorizing the use of those 100transceivers, and install those 100 transceivers in an opticalcommunications network. Data regarding that license can be transmittedto and stored on those transceivers to regulate their use.

In some implementations, a license may authorize the use of a particularnumber of licenses, regardless of the specific transceivers that areused at any given time. For example, if a user wishes to deploy 100transceivers, he may obtain a license authorizing the use 100transceivers, and deploy 100 transceivers in an optical communicationsnetwork. Data regarding that license can be transmitted to and stored onthose transceivers to regulate their use. Subsequently, the user canreplace one or more of those transceivers with other transceivers, solong as the total number of deployed transceivers does not exceed 100.In some implementations, this may be referred to as a “floating”license.

In some implementations, an edge transceiver's license can be verifiedcontinuously, periodically, or intermittently (e.g., by the centralsoftware 111 or some other component). In some implementations, an edgetransceiver that does not comply with the license can be remotelydisabled (e.g., by the central software 111 or some other component)until an updated license is provided or the edge transceiver isreconfigured to comply with the license.

After processing the request, the hub transceiver 2102 transmits amessage to the edge transceiver 2104 a confirming that the request wasprocessed (block 2116) in a manner similar to that described above. Ifthe request was successfully fulfilled by the hub transceiver 2102, themessage can include an indication that the requested bandwidth wassuccessfully allotted or one or more optical subcarriers were assignedto the edge transceiver 2104 a. If the request could not be fulfilled bythe hub transceiver, for example, by control circuit 1161 in the hubtransceiver, the message can include an indication that the requestedsubcarrier assignment or bandwidth allocation could not be completed,and an indication of one or more one or more modifications to therequest that would enable the request to be fulfilled (e.g., anindication of one or more alternative optical subcarriers that areavailable for assignment or, for example, another amount of bandwidth isavailable, such as a lesser amount than that requested).

Upon receiving a message confirming that the requested opticalsubcarrier was successfully assigned or the requested bandwidth had beenallotted to the edge transceiver 2104 a, the edge transceiver 2104 a cantransmit data to the hub transceiver 2102 using the assigned opticalsubcarriers (e.g., as described with respect to FIGS. 3 and 10 ) (block2218).

Alternatively, upon receiving a message indicating that the requestedbandwidth could not be allotted or the requested optical subcarriercould not be assigned could not be assigned to the edge transceiver 2104a, the edge transceiver 2104 a can modify its request and transmit themodified request to the hub transceiver 2102 (e.g., repeating step2110).

Some or all of the process 2100 can be repeated until each of the edgetransceivers 2104 a-2104 n has been allotted a respective bandwidth orassigned a particular optical subcarrier assigned to each such edgetransceiver.

As described above with respect to FIG. 21 , in some implementations,each of the edge transceivers 2102 a-2102 n can monitor the opticalcommunications network for the presence of the hub transceiver 2102.Detecting the presence of hub transceivers will next be described withreference to FIGS. 22A to 22E.

As noted above, the frequency of light or an optical signal output localoscillator laser 1110 (FIG. 8 ) or shared laser 908 (FIG. 9C) can betuned based on an output from control circuit 1161 or DSP 1150. As shownin FIG. 22A, assuming that there are multiple hub transceivers that areoptically coupled to a given one of edge transceivers 2104, the edgetransceiver, in one example, receives optical subcarriers output from afirst hub transceiver that define a range of frequencies, SC Group 1,based on a difference in frequency between the highest subcarrierfrequency and the lowest subcarrier frequency in that group ofsubcarriers. Optical subcarriers output from a second hub transceiverdefine a range of frequencies, SC Group 2, based on a difference in thehighest subcarrier frequency and the lowest subcarrier frequency in thegroup of subcarriers output from the second hub. The first and secondhub transceivers are similar to the hub transceivers described above.Typically, the laser in the first hub transceiver has a frequency fHub1,which is central or in the middle of SC Group 1, and the laser in thesecond hub transceiver has a frequency fHub2 that is central or in themiddle of SC Group 2.

As shown in FIG. 22B, the edge transceiver laser, such as laser 908 or1110, described above may be tuned in a manner described above to changein frequency of light output thereof over a range of frequencies, suchas the C-Band (1530-1565 nm). In one example, the light output fromlaser 908 or 1110 is scanned or tuned in a step-wise manner, such thateach step is the same. That is, in one example, the frequency of thelocal oscillator light (fLeaf) output from laser 908 or 110 isincreased, starting at or near the lowest frequency of the tunablefrequency range, such as the C-Band, to the highest frequency or afrequency near the highest frequency, in steps or increments of 50 GHzor some other frequency increment. In practice, the step size can besmaller or larger, depending on the implementation. In another example,the steps or increments may be non-uniform or not equal to one another.Also, the scan may be made by decreasing the local oscillator frequencyin increments instead of increasing the local oscillator frequency, asdescribed above. In the example shown in FIG. 22B, fLeaf is initiallyset to frequency f1, and then increased in a step-wise manner tofrequency f8, such that the fLeaf remains fixed for a predeterminedperiod of time at each of frequency f1-f8 before advancing to the nextfrequency. Such period of time is sufficient for circuitry describedabove in the receiver portion of the transceiver to detect the AMmodulation of the subcarriers output from the hub transceiver.Accordingly, a number of frequencies (e.g., a number of frequencysubsets) are scanned.

In another example, the local oscillator frequency may be continuouslyscanned or tuned within frequency ranges, such as ranges betweenfrequencies f1 and f2; f2 and f3; f3 and f4; f5 and f6; and f7 and f8.In a further example, the local oscillator frequency may be scanned ortuned with spectral gaps between successive ranges. Accordingly, in theexample shown in FIG. 22B, the local oscillator frequency may be scannedbetween frequencies f1 and f2; f3 and f4; f5 and f6; and f7 and f8,whereby the ranges between f2 and f3; f4 and f5; and f6 and 7 areskipped. Such skipping may be employed to realize a faster scan orsearch of the optical outputs of the hub or hubs.

When the frequency of light output laser 908 or 1110 is within SC Group1, the light output from laser 908 or 1110 will “beat” with light atsuch subcarrier frequency. In another example, when such localoscillator light is within a predetermined frequency range of the lightoutput from the hub transceiver, such beating may occur. As a result,the circuitry described above in FIGS. 8, 9A, and 9B, in one example,detects the amplitude modulation of the incoming light based on coherentdetection. Data associated with such modulation, includes, for example,an identification of hub transceiver as well as the frequency of lightoutput by the laser provided in the hub. In addition, the data mayinclude instructions for tuning laser 908 or 1110 to have a centerfrequency (fLeaf) at which a group of subcarriers output from the huband designated for the edge or leaf node may be detected in a mannersimilar to that described above with reference to FIGS. 8 and 15 . Inthe example shown in FIG. 22C, the edge or leaf transceiver has abandwidth sufficient to detect and process four subcarriers output fromthe hub transceiver, two subcarriers on either side of fLeaf.Instructions included in the data associated with the above-describedamplitude modulation may identify one or more of these subcarriers foruse by the leaf or edge node or that the edge node should communicatewith another hub.

The edge node may detect amplitude modulation of the subcarriers outputfrom the second hub and have frequencies in SC Group 2 in a mannersimilar to that described above. In one example, after the subcarriersoutput from both hubs have been detected, the edge node may communicatewith the optical gateway in a manner described above (see FIG. 7 ) withrequest for the optical gateway to identify which hub the edge nodeshould communicate with. The optical gateway, in turn, providesinformation identifying which subcarriers have been designated for theedge node, and laser 908 or 1110 in the edge node is tuned accordinglyfor processing of the information or data carried by such subcarriers ina manner similar to that described above in connection with FIGS. 7 and8 .

In some implementations, an edge transceiver laser can scan a particularfrequency range according to a particular step size. For example, anedge transceiver laser, such as laser 908 or 1110, can tune to aparticular frequency in the frequency range (e.g., using a localoscillator) and measure the power of the signal at that frequency (e.g.,using one or more of the components of the receiver optics and A/D block1100 and Rx DSP 1150, as shown in FIGS. 8, 9A, and 9B). Further, theedge transceiver can repeat the measurement process for multipledifferent frequencies within the frequency range (e.g., by increasing ordecreasing the tuned frequency according to the step size). As notedabove, in some implementations, an edge transceiver can scan aparticular frequency range according to a step size such as 50 GHz.However, in practice, the step size can be smaller or larger, dependingon the implementation.

FIG. 23D shows the power spectrum 2200 across a particular frequencyrange (e.g., an example “full” or “complete” frequency range scanned bythe edge transceivers), and FIG. 22E shows the power spectrum 2200across a subset of that frequency range (e.g., indicated by the box2250). In this example, the horizontal axis of the power spectrum 2200indicates the frequency of the received signal, and the vertical axisindicates that power of the signal at the frequency.

The power spectrum can be used to identify a carrier signal or otherfrequencies of optical subcarriers output from a hub transceiver. Forinstance, in the example shown in FIG. 22E, the power spectrum 2200includes three peaks 2202 a-2202 c, and several valleys 2204 a-2204 d.The valleys 2204 a-2204 d indicate a relative absence of power inparticular frequency bands (e.g., indicating that the carrier signal ofthe hub transceiver is unlikely to be in those frequency bands).

In contrast, the peaks 2202 a-2002 c indicate a relatively higher powerin particular frequency bands, which may associated with the modulatedoptical signal output froma hub transceiver or some other localized peakin power (e.g., an amplified spontaneous emission (ASE) that does notcorrespond to a carrier signal). In some implementations, an edgetransceiver can distinguish between a carrier signal of a hubtransceiver and other signals (e.g., an ASE) based on the power of thereceived signal in particular frequency bands. For instance, circuitrydescribed above in the edge receiver can determine that the frequency orfrequency band having the highest power is likely to be a carrier signalfrom a hub transceiver, whereas frequency or frequency bands havingcomparatively lower power is likely to be an extraneous signal (e.g., anASE). As an example, as shown in FIG. 22E, the edge transceiver candetermine, based on the power spectrum 2200, that the frequency band forpeak 2202 b is likely to contain a carrier signal from a hubtransceiver, whereas the peaks 2202 a and 2202 c are likely to be ASEs.

In some implementations, an edge transceiver can distinguish betweenfour different states based on the power spectrum, and based on whethera beacon message was received using a particular frequency or frequencyband.

For example, a first state can correspond to the presence of a carriersignal from the hub transceiver 2102. In some implementations, the firststate can be identified by identifying, using the circuitry shown inFIG. 9A, for example, a peak in the power spectrum that is above aparticular first threshold power (e.g., an empirically determinedthreshold value), and determining that a beacon message was received inthe corresponding frequency or frequency band. In the example shown inFIG. 22E, the peak 2202 b could correspond to the first state.

As another example, a second state can correspond to the presence ofsubcarriers from another hub transceiver, as detected in a mannersimilar to that described above with respect to FIGS. 22A-22C, that isnot compatible with the edge transceiver (e.g., a “legacy” hubtransceiver). In some implementations, the first state can be identifiedby identifying a peak in the power spectrum that is above a particularfirst threshold power (e.g., an empirically determined threshold value),and determining that a beacon message was not received in thecorresponding frequency or frequency band.

As another example, a third state can correspond to the presence of anASE (e.g., implying that a line system passband is open, but that a hubtransceiver has not been powered up yet). In some implementations, thethird state can be identified by identifying a peak, in a manner similarto that described above, in the power spectrum that is less than thefirst threshold power but greater than a second threshold power (e.g.,another empirically determined threshold value). In the example shown inFIG. 22E, the peaks 2202 a and 2202 c could correspond to the thirdstate.

As another example, a fourth state can correspond to an unusedcommunications channel. In some implementations, the third state can beidentified by identifying a peak in the power spectrum in a mannersimilar to that described above that is less than a third thresholdpower (e.g., another empirically determined threshold value). In theexample shown in FIG. 22E, the valleys 2204 a-2204 d correspond to thefourth state.

In some implementations, an edge transceiver can distinguish between thefour different states based on a relative comparison of the powers ofthe identified peaks and valleys. For example, the edge transceiver canidentify the N peaks having the greatest power among the peaks, andidentify those peaks as potentially including a beacon message from ahub transceiver (e.g., either the first state or the second state). Uponconfirming that a beacon message was received in one of the frequenciesor frequency bands corresponding to a particular peak of the N peaks,the edge transceiver can identify that peak as corresponding to thefirst state. Further, upon confirming that a beacon message was notreceived in one of the frequencies or frequency bands corresponding tothe other peaks of the N peaks, the edge transceiver can identify thosepeaks as corresponding to the second state. Further, the edgetransceiver can identify the peaks other than the N peaks ascorresponding to the third state or the fourth state.

As described above with respect to FIG. 21 , in some implementations,the hub transceiver 2102 can broadcast a beacon message by employing AMmodulation, for example, to multiple ones of the edge transceivers 2104a-2104 n (or to all the edge transceivers 2104 a-2104 n) concurrently.For instance, in another example, the beacon message can be broadcast toeach of the edge transceivers 2104 a-2104 n using a common OOB basebandcarrier, such that each of the edge transceivers 2104 a-2104 n receivesa respective copy of the beacon message concurrently (or substantiallyconcurrently).

An example depiction of a broadcast transmission of a beacon messagefrom a hub transceiver is shown in FIG. 23A during an initializationphase, for example, when an edge transceiver, such as edge transceiver2104 a, is initially coupled to the hub node. As shown in FIG. 23A andin one example, the beacon message may constitute first and secondamplitude modulations imparted across subcarrierss 1-16 (collectivelylabeled as 2302) output from a hub transceiver. Such amplitudemodulation is generated in a manner similar to that described above,such as in connection with FIGS. 3, 4A, 5, and 6A, and are representedby rectangles 2304-1 and 2304-2 on each of the optical subcarriers 1-16.in FIG. 23A. In one example, the first amplitude modulation may have anassociated first frequency, such as a frequency in a range of 5 MHz to 6MHz, and the second modulation has an associated second frequency, suchas a frequency in a range of 3 MHz to 4 MHz. In a further, example, thefirst modulation carries data indicative of first control informationintended for the optical gateway, and, accordingly, is detected by theoptical gateway in a manner similar to that described above inconnection with FIG. 7 . In an implementation, the second modulationcarries data indicative of second control information intended for theedge nodes, and, accordingly, is detected by the receiver in the edgenode transceiver in a manner similar to that described above inconnection with FIGS. 8, 9A, and 9B. In some implementations, theidentity of the center frequency or position of the hub laser can beprovided in a beacon message that is broadcast by the hub transceiver2102.

In the edge node, local oscillator light, supplied from a laser, such aslaser 908 (FIG. 9C) or 1110 discussed above, may be tuned in a mannersimilar to that described above to detect the second amplitudemodulation embedded over or imparted onto optical subcarriers 1-16 (seeFIGS. 8, 9A, and 9B). In some implementations, circuitry in the edgenode, such as control circuit 1161, receive the control informationassociated with the second amplitude modulation, and, based on thereceived control information, control circuit 1161 may generate amessage that is used to amplitude modulate a subcarrier that istransmitted back to the hub transceiver. The message may include arequest for an allotment of bandwidth or capacity of an assignment ofone or more subcarriers to the edge node. In one example, a transmitterlaser, such laser 908 (see FIGS. 4A and 9C) may be tuned in a mannernoted above to have a frequency, such that upon modulation, theresulting subcarrier(s) may be detected by the hub by coherentdetection.

FIG. 23B shows a power spectral density plot showing a first subcarrier,2307-1, that carries control information, such as the bandwidthallotment request in the form of an amplitude modulation represented byrectangle 2308-1. A second optical subcarrier, 2307-2, is shown that maybe amplitude modulated to carry control information to the opticalgateway. Rectangle 2308-2 represents such amplitude modulation of thesecond optical carrier 2307-2.

FIG. 34 illustrates circuitry, which, in one example, is employed togenerate the subcarriers 2307-1 and 2307-2 and respective amplitudemodulations thereof, 2308-1 and 2308-2 during the initialization phase.Namely, as noted above with respect to FIGS. 5 and 14 , inverse FastFourier Transform circuits 1010-1 and 1010-2 may receive inputs fromcircuit block 903-2 to generate polarization multiplexed signal, whichconstitutes a subcarrier, also referred to above as an out of band (OOB)signal. In the example shown in FIG. 34 , instead of supplying signalfrom circuit block 903-2 in a Tx DSP provided in the edge node, signalsindicative of an amplitude modulation carrying control data orinformation are input to IFFTs 1010-1 and 1010-2. As a result, insteadof a polarization multiplexed signal or optical subcarrier being output,an amplitude modulated optical subcarrier 2307-1 and 2307-2 is output.

As with the polarization multiplexed optical subcarrier described above,the amplitude modulated optical subcarrier has less power and a narrowerspectral width than optical subcarriers associated with transmission ofinformation indicative of user data.

In one example, multiple edge nodes may transmit their respectiveoptical subcarriers 2307-1 and/or 2307-2, as in a “party line.” In someimplementations, the amplitude modulation of each edge node mayinterfere or collide with one another. Accordingly, in one example, theedge nodes may continue to periodically retransmit their respectivecontrol information including the bandwidth allocation message until anacknowledgment is received from the hub node confirming that therequested optical subcarrier(s) or bandwidth was successfully assignedor allocated to the edge transceiver 2104 a. In another example, themessages may be time division multiplexed to avoid such collisions.

In the hub, detection of AM modulation of subcarriers received from theedge node is similar to that described in the edge node (see FIGS. 8,9A, and 9B). After receiving the bandwidth allotment or opticalsubcarrier assignment request from the edge node, a control circuit 1161in the hubmay assign one or more optical subcarriers or the bandwidthassociated with such subcarriers to the requesting edge node. The hubnode may then collectively modulate optical subcarriers 1-16 outputtherefrom in a manner similar to that described above to transmit dataindicative of such assignment information (see FIGS. 4A, 4B, 5, and 6A).The edge node receives such optical subcarriers and detects theassignment information in a manner similar to that noted above. Based onsuch assignment information, control circuit 1161 in the edge node mayprovide signal to activate those portions of the edge node Rx and TxDSPs for receiving/processing and transmitting the assigned opticalsubcarriers, and de-activate those portions of Rx and Tx DSP that wouldotherwise process data associated with the un-allocated opticalsubcarriers (see FIGS. 6B and 6C). Further based on the assignmentinformation, the edge node laser (either laser 908 shown in FIG. 4A orthe shared laser in FIG. 9C) is tuned in a manner described above toprovide optical subcarriers having the frequencies indicated by theassignment information.

Accordingly, in the example shown in FIG. 23B, the assignmentinformation provided by the hub node designated subcarriers 3 and 4 to aparticular edge node. As a result, the corresponding power density plot24-2 shows such optical subcarriers. Such subcarriers may not betransmitted prior to assignment by the hub node. Accordingly, powerdensity plots show non-assigned subcarriers 1 and 2 (plot 24-2) inphantom. In addition, subcarriers 1-4 are shown in phantom in plot 24-1prior to receiving the bandwidth assignment from the hub. In addition,after processing of the beacon and bandwidth assignment message,subcarriers 2307-1 and 2307-2 may not be required and are optionally nottransmitted post-bandwidth assignment.

An example depiction of subcarrier received by the hub transceiver isshown in FIG. 23C. As shown in FIG. 23C, the hub transceiver receivesoptical subcarriers 2302 (in this example, the optical subcarriers 1-16)transmitted by the edge transceivers, each such optical subcarriercarrying data. In a further example, the hub transceiver receivesrequest messages and/or telemetry data from one or more of the edgetransceivers according to one or more respective optical subcarriersincluding, for example, optical subcarriers 2307-1 and 2307-2, shown asoptical subcarriers 2308.

In the example shown in FIG. 23C, based on assignment instructionsreceived from the hub node, optical subcarriers 9, 11, 13, and 15 aretransmitted from a first edge node; optical subcarriers 7, 5, and 3 arereceived from a second edge node; optical subcarrier 1 is transmittedfrom a third edge node; optical subcarrier 2 is transmitted from afourth edge node; optical subcarriers, 4, 6, and 8 are transmitted froma fifth edge node; and optical subcarriers 10, 12, 14, and 16 aretransmitted from a sixth edge node.

As described above with respect to FIG. 21 , a hub transceiver can allotbandwidth or assign one or more optical subcarriers to each of the edgetransceivers for use in transmitting data on the optical communicationsnetwork. Example allotment techniques are shown and described withrespect to FIGS. 24A and 24B. For ease of explanation, “assignment ofsubcarriers” or “allotment of subcarriers” and related terms refer tothe assignment or allocation of bandwidth associated with thesubcarriers or the data carried by the subcarriers.

In some implementations, a hub transceiver initially can assign abandwidth or data associated with multiple contiguous opticalsubcarriers to a particular edge transceiver. The first opticalsubcarrier can be designated as a data optical subcarrier (e.g., anoptical subcarrier that includes information indicative of user data),whereas the one more optical subcarriers following the data opticalsubcarrier can be designated as idle optical subcarriers (e.g., opticalsubcarriers that do not include an encoded version of the data, such asa “blank” optical subcarrier having a carrier signal only). Such idlesubcarriers may carry a random bit sequence (PRBS), such as thatgenerated by a PRBS generator circuit or may carry idle packets, whichinclude a predetermined sequence of bits, such as all “1”s or all “0”s,as noted above.

For instance, in the example shown in FIG. 24A, edge transceivers 1-4have been assigned four continuous optical subcarriers each. For eachedge transceiver, the leading optical subcarrier is designated as a dataoptical subcarrier, and the trailing three optical subcarriers aredesignated as idle optical subcarriers.

This can be beneficial, for example, as it maintains a degree ofseparation between each of the data optical subcarriers that areassigned to the edge transceivers, which may increase the compatibilitywith the optical communications network or robustness of the opticalcommunications network against interference.

When some or all of available optical subcarriers are allotted (e.g.,either as data or idle optical subcarriers), the hub transceiver canre-assign at least some of the idle optical subcarriers for use by newedge transceivers that are added to the network. Further, the idleoptical subcarriers can be re-assigned in such a way that a certaindegree of separation is maintained between the resulting data opticalsubcarriers. Such re-assignment in the uplink direction from the edgenodes to the hub node can be achieved by turning on and off subcarriers,as discussed above in connection with FIGS. 6A and 6B. Further, in thereceiver portions of the edge transceiver, similar circuitry may beprovided at the outputs of FFTs 1210-1 and 1210-2 in FIG. 15 to zero outand thereby frequency components associated with subcarriers carryingdata not intended for a particular subcarrier. In addition, suchcircuitry may selectively allow the frequency components to be furtherprocessed, such that information associated therewith is output by theedge node for which the information is intended. In this example,therefore, bandwidth and data may be dynamically assigned to the edgenodes. In a further example, signals for controlling the circuitrydescribed above in FIGS. 6A and 6B may be provided by control circuit1161 in a manner similar to that described above. For ease ofexplanation, a given edge node is referred to herein as being assignedor allotted subcarriers even though the photodetectors of that edge nodemay also receive optical subcarriers other than the allottedsubcarriers. Data or information associated with such un-allottedsubcarriers is blocked or not decoded, in one example, in a mannersimilar to that described above.

In the example shown in FIG. 24A, once all of the optical subcarriers1-16 have been assigned to the edge transceiver 1-4, the hub transceivercan begin re-assigning the idle optical subcarriers for use by new edgetransceiver 5-8. For example, the hub transceiver can re-assignsubcarriers 7 and 8 to a new edge transceiver 5 (where the opticalsubcarrier 7 is a data optical subcarrier, and the optical subcarrier 8is an idle optical subcarrier). Similarly, the hub transceiver canre-assign subcarriers 11 and 12 to a new edge transceiver 6 (where theoptical subcarrier 11 is a data optical subcarrier, and the opticalsubcarrier 12 is an idle optical subcarrier), re-allot subcarriers 3 and4 to a new edge transceiver 7 (where the optical subcarrier 3 is a dataoptical subcarrier, and the optical subcarrier 4 is an idle opticalsubcarrier), and re-allot subcarriers 15 and 17 to a new edgetransceiver 8 (where the optical subcarrier 15 is a data opticalsubcarrier, and the optical subcarrier 16 is an idle opticalsubcarrier). Accordingly, the resulting data optical subcarriers (e.g.,optical subcarriers 1, 3, 5, 7, 9, 11, 13, and 15) are still separatedfrom one another by at least one idle optical subcarrier between them.

When a total separation of data optical subcarriers is no longerfeasible (e.g., the number of edge transceivers exceeds half of thetotal number of optical subcarriers available for allotment), the hubtransceiver can re-allot any of the remaining idle optical subcarriersfor use by new edge transceivers that are added to the network. This isbeneficial, for example, as it enables the hub transceiver to maximizeusage of the available optical subcarriers as needed.

For instance, in the example shown in FIG. 24A, after re-allottingoptical subcarriers to accommodate the edge transceiver 5-8, the hubtransceiver can re-allot any remaining idle optical subcarriers for useby new edge transceiver 9-16. This re-allotment can be performed untilno more idle optical subcarriers remain.

In some implementations, optical subcarriers can be allotted accordingto one or more specific rules based on the capabilities of the edgetransceivers. As an illustrative example, given 16 spectrally contiguousoptical subcarriers (SC1-SC16), optical subcarriers can be allotted totransceivers having a first bandwidth capability or capacity (e.g., 100Gbit/s) by searching for four contiguous optical subcarriers starting onSC5, SC9, SC1, and SC13, in that order.

Further, optical subcarriers can be allotted to transceivers having asecond, lower bandwidth capability (e.g., 50 Gbit/s) by searching forblocks of four contiguous optical subcarriers with an odd/even pair ofoptical subcarriers free. The search order can be, for example, SC5,SC7, SC9, SC11, SC3, SC1, SC13, and SC15, in that order. If there are nopartially filled blocks, the same search order for transceivers havingthe first bandwidth capability (e.g., 100 Gbit/s) can be used (e.g., bysearching for four contiguous optical subcarriers starting on SC5, SC9,SC1, and SC13, in that order).

Further, optical subcarriers can be allotted to transceivers having athird, lower bandwidth capability (e.g., 25 Gbit/s) by searching forblocks of four contiguous optical subcarriers with a single opticalsubcarrier free. If there are no so such blocks, the same search orderfor transceivers having the second bandwidth capability (e.g., 50Gbit/s) can be used (e.g., by searching for partially filled odd/evenpairs of optical subcarriers). Finally, if there are no partially filledodd/even pairs of optical subcarriers, the same search order fortransceivers having the first bandwidth capability (e.g., 100 Gbit/s)can be used (e.g., by searching for four contiguous optical subcarriersstarting on SC5, SC9, SC1, and SC13, in that order).

FIG. 24B shows an example process 2400 for allotting optical subcarriersto edge transceivers according to one or more specific rules based onthe capabilities of the edge transceivers (e.g., one or more of therules discussed above). The process 2400 can be performed, for example,by a hub transceiver upon receipt of a request for allotment of one ormore optical subcarriers by an edge receiver.

According to the process 2400, the hub transceiver determines whetherthere is sufficient bandwidth across each of the groups of opticalsubcarriers (e.g., whether there is enough bandwidth to satisfy therequirements of each of the edge transceivers that are requesting orhave requested allocation of optical subcarriers from the hubtransceiver). If not, the hub transceiver generates a notification oralarm indicating that there is insufficient bandwidth (e.g., anotification or alarm that is presented to a user) (block 2404).

Alternatively, if there is sufficient bandwidth across the groups, thehub transceiver determines the type of configuration of the edgetransceiver that made the request. For example, the hub transceiver candetermine whether the request was made by an edge transceiver having afirst type of configuration (e.g., a 100 Gbit/s edge transceiver), asecond type of configuration (e.g., a 50 Gbit/s edge transceiver), or athird type of configuration (e.g., a 25 Gbit/s edge transceiver) (blocks2406 a-2406 c, respectively).

If the edge transceiver has the first type of configuration (e.g., a 100Gbit/s edge transceiver), the hub transceiver can allocate opticalsubcarriers to the edge transceiver according to the correspondingassignment protocol discussed above (block 2408). For example, given 16spectrally contiguous optical subcarriers (SC1-SC16), opticalsubcarriers can be allotted to transceivers having a first bandwidthcapability or capacity (e.g., 100 Gbit/s) by searching for fourcontiguous optical subcarriers starting on SC5, SC9, SC1, and SC13, inthat order.

If the edge transceiver has the second type of configuration (e.g., a 50Gbit/s edge transceiver), the hub transceiver can allocate opticalsubcarriers to the edge transceiver according to the correspondingassignment protocol discussed above (block 2410). For example, the hubtransceiver can initially determine whether there is sufficientbandwidth in any groups of optical subcarriers to fulfill the request(block 2410). If so, optical subcarriers can be allotted to transceivershaving a second, lower bandwidth capability (e.g., 50 Gbit/s) bydetermining whether an odd/even pair of optical subcarriers is requiredby that edge transceiver (block 2412) and if so, whether any such pairsare available (block 2414). If so, the hub transceiver can search forblocks of four contiguous optical subcarriers with an odd/even pair ofoptical subcarriers free (block 2416). The search order can be, forexample, SC5, SC7, SC9, SC11, SC3, SC1, SC13, and SC15, in that order.If there are no partially filled blocks, the same search order fortransceivers having the first bandwidth capability (e.g., 100 Gbit/s)can be used (e.g., by searching for four contiguous optical subcarriersstarting on SC5, SC9, SC1, and SC13, in that order).

If the edge transceiver has the third type of configuration (e.g., a 25Gbit/s edge transceiver), the hub transceiver can allocate opticalsubcarriers to the edge transceiver according to the correspondingassignment protocol discussed above (block 2418). For example, the hubtransceiver can allot optical subcarrier to transceivers having a third,lower bandwidth capability (e.g., 25 Gbit/s) by determine whether thereare any groups of optical subcarriers having a partially “filled”odd/even pair (e.g., continuous optical subcarriers where one opticalsubcarrier has already been allotted, and the other optical subcarrierhas not yet been allotted) (block 2418).

If so, the hub transceiver can allocate an optical subcarrier based onthe allocation order described above (e.g., block 2420). For example,the hub transceiver can search for blocks of four contiguous opticalsubcarriers with a single optical subcarrier free. If there are no sosuch blocks, the same search order for transceivers having the firstbandwidth capability (e.g., 50 Gbit/s) can be used (e.g., by searchingfor partially filled odd/even pairs of optical subcarriers).

Alternatively, if there are no partially filled odd/even pairs ofoptical subcarriers, the same search order for transceivers having thefirst bandwidth capability (e.g., 100 Gbit/s) can be used (e.g., bysearching for four contiguous optical subcarriers starting on SC5, SC9,SC1, and SC13, in that order) (block 2416).

During the process 2400, if the hub transceiver determines that there issufficient total amount of bandwidth to fulfill the request, but thatthere are no available optical subcarriers or groups of opticalsubcarriers that fulfill the assignment protocol or rules (e.g., thearrangement of available optical subcarriers does not satisfy theassignment protocol or rules), the hub transceiver can generate anotification or alarm to a user indicating that a “defragmentation” ofthe optical subcarriers may be required (e.g., a re-assignment of theoptical subcarriers to the edge transceivers to consolidate assignedoptical subcarriers in certain groups to the consolidate unassignedoptical subcarriers in other groups). In some implementations, the hubtransceiver can automatically perform the defragmentation (e.g., byreassigning the optical subcarriers to the edge transceivers).

In some implementations, an edge transceiver can transmit data usingmultiple optical subcarriers concurrently in order to enable backwardscompatibility with legacy network devices (e.g., legacy devices thatrequire that signals have a particular power signature that spansmultiple optical subcarriers). For example, referring to FIG. 25 (leftpane), a legacy device may require that a signal have a “domed” or“curved” power signature (e.g., having a higher power in a center of aparticular frequency range, and lower power towards the peripheries ofthe frequency range). Further, this power signature could span acrossseveral optical subcarriers.

However, if the power signal does not have this power signature, thelegacy device may not recognize the optical subcarrier signals as avalid legacy signal. For example, referring to FIG. 25 (center pane), anedge transceiver could generate a signal by transmitting data using fourcontiguous optical subcarriers (denoted as SC1-SC4), such that the widthof the power signature approximates the power signature that isrecognized by the legacy device. However, in this example, the edgetransmission module transmits the signal according to a similar poweracross each of the optical subcarriers (e.g., resulting in anapproximately rectangular power signal, rather than a domed powersignature). Thus, a legacy device may not recognize the signal as avalid signal.

To improve capability for the legacy device, the edge transceiver caninstead transmit a signal that mimics the power signature that isrecognized by the legacy device. For example, referring to FIG. 25(right pane), the edge transceiver can generate a signal that has ahigher power in the center optical subcarriers (e.g., SC2′ and SC3′),and a comparatively lower power in the peripheral optical subcarriers(e.g., SC1′ and SC4′). Thus, the resulting signal can be recognized bythe legacy device.

Moreover, if one of subcarriers, if one of subcarriers, such as SC2′ isnot assigned to carry information indicative of user data, suchsubcarrier may still carry random data, e.g., a PRBS, or blank frames asnoted above, instead of omitting such subcarrier in order, for example,to maintain power levels in the system. In that case SC2′ may be areferred to as an idel subcarrier, as described herein.

As described above (e.g. with respect to FIG. 21 ), in someimplementations, at least some of the transceivers can be initiallyidentical to one another (e.g., initially identical in configuration).In some implementations, these transceivers can be re-configured tofunction as a hub transceiver or an edge transceiver as a part of aconfiguration process (e.g., once the transceivers have establishedcommunications with one another). This can be useful, for example, as itenables a single type of transceiver (e.g., a “universal” transceiverthat can function as both a hub transceiver and as an edge transceiver)to be deployed at several locations on the network. Depending on theconfiguration of the network, each of the transceivers can bedynamically assigned (or reassigned) the role of a hub transceiver or anedge transceiver (e.g., to perform one or more of the operationsdescribed herein). Accordingly, the transceiver need not be physicallyreplaced when the network is reconfigured and/or when its role in thenetwork is changed.

As an example, FIG. 29 shows an example process 2900 for dynamicallyconfiguring a transceiver as a hub transceiver or an edge transceiver.In some implementations, the process 2900 can be performed by atransceiver has not yet been assigned the “role” of a hub transceiver oran edge transceiver, or by a transceiver that was previously assignedthe role of a hub transceiver or an edge transceiver. A role can be, forexample, a configuration of the transceiver (e.g., in software,hardware, or both) and/or a function or category functions assigned tothe transceiver with respect to the optical communications network.

According to the process 2900, the transceiver conducts a scan of thechannels and sub channels of the optical communication network toidentify the presence of any hub transceivers that are transmittingbeacon messages (block 2902). As an example, the transceiver can scanone or more optical subcarriers for the presence of a beacon message(e.g., a beacon message transmitted by amplitude modulating signals onmultiple optical subcarriers, as described with respect to FIGS.22A-22C).

Upon detecting a beacon message, the transceiver attempts to connect tothe hub transceiver that is transmitting the beacon message, negotiateone or more communications channels with that hub transceiver, andauthenticate its identify with that hub transceiver and/or authenticatethe identity of that hub transceiver (block 2904) using the AMmodulations discussed above and circuitry, such as control circuit 1161in the hub and edge nodes. In some implementations, this can includeperforming one or more of the operations described with respect to FIG.21 (e.g., transmitting a message requesting assignment of one or more ofoptical subcarriers to the hub transceiver, receiving a confirmationthat one or more optical subcarriers have been assigned from the hubtransceiver, and transmitting data according to the assigned opticalsubcarriers). In some implementations, the transceiver can alsodetermine whether the beacon message has transmitted by a blacklistedhub transceiver (e.g., a hub transceiver to which it should notconnect), and if so, terminate the connection with that hub transceiver.

Upon completion of these operations, the transceiver can configureitself as either a hub transceiver (block 2906) or an edge transceiver(block 2908).

In some implementations, the transceiver can configure itself as an edgetransceiver by default. For example, the transceiver can connect to thehub transceiver that is transmitting the beacon message, negotiate oneor more communications channels with that hub transceiver, andauthenticate its identify with that hub transceiver and/or authenticatethe identity of that hub transceiver. Upon completion of theseoperations, the transceiver can function as an edge transceiver andperform one or more other associated operations described herein.

In some implementations, the transceiver can configure itself as eithera hub transceiver or a hub transceiver, depending on its ownconfiguration and the configuration of the hub transceiver that istransmitting the beacon message. For example, the transceiver can assumethe role of an edge transceiver, and the hub transceiver (e.g., thetransceiver that had transmitted the beacon message) can retain the roleof a hub transceiver. In some implementations, the transceiver canassume the role of a hub transceiver, and the hub transceiver (e.g., thetransceiver that had transmitted the beacon message) can switch to therole of an edge transceiver.

In some implementations, transceivers can be assigned the role of anedge transceiver or hub transceiver based on the number of opticalsubcarriers that have been allotted to each of the transceivers. Forexample, the transceiver that has been allotted a greater number ofoptical subcarriers can be assigned the role of a hub transceiver, andthe transceiver that has been allotted a fewer number of opticalsubcarriers can be assigned the role of an edge transceiver. In someimplementations, the transceivers can dynamically swap roles (e.g., whenthe allotment of optical subcarriers is modified).

In some implementations, if the transceivers are each allotted the samenumber of optical subcarriers, the transceivers can be assigned rolesbased on other factors. For example, each transceiver may be assigned arespective identifier (e.g., a numerical index value), and thetransceiver having the lowest identifier can be assigned the role of thehub transceiver, or vice versa.

In some implementations, a remote device (e.g., the central software111) can assign roles to transceivers. For example, in someimplementations, the central software 111 can override the assignment ofroles according to the process 2900 (e.g., by providing supersedingassignments).

Alternatively, if the transceiver is unable to complete the operationsdescribed with respect to block 2904 (e.g., the transceiver wasunsuccessful in connecting with the hub transceiver, negotiating one ormore communications channels with the hub transceiver, authenticatingits identify with that hub transceiver, and/or authenticating theidentity of that hub transceiver), the transceiver enters a “receiver”mode (block 2910). While in the receiver mode, the transceiver laser 908or 1110 scans through a spectrum of signal frequencies being transmittedon the optical communications network, and determines whether a beaconmessage is being transmitted on the optical communication network usingone or more of those frequencies.

As noted above with respect to FIGS. 22A-22C, upon detecting anotherbeacon message, the transceiver attempts to connect to the hubtransceiver that is transmitting the beacon message, negotiate one ormore communications channels with that hub transceiver, and authenticateits identify with that hub transceiver and/or authenticate the identityof that hub transceiver (block 2904).

Alternatively, if the transceiver does detect a beacon message after aperiod of time (e.g., after a certain number of frequencies or a certainrange of frequencies has been scanned, or after a certain amount of timehas elapsed), the transceiver switches to a “transmitter” mode (block2912). While in the transmitter mode, the transceiver listens or scansits laser, such as laser 1110 or 908, to detect any signals beingtransmitted on the optical communications network, and identifies one ormore channels that are not currently being used by other transceivers(e.g., one or optical subcarriers that are not being used to transmitdata). The transceiver then transmits a message using the unused channel(e.g., a beacon message, as described above with respect to FIG. 21 ).

Upon receiving a response to the transmitted message (e.g., from an edgetransceiver), the transceiver attempts to connect to the transceiverthat transmitted the response, negotiate one or more communicationschannels with that transceiver, by way of exchanging AM signals as notedabove, and authenticate its identify with that transceiver and/orauthenticate the identity of that transceiver (block 2904). Uponsuccessfully completing these operations, the transceiver can configureitself as either a hub transceiver (block 2906) or an edge transceiver(block 2908). In some implementations, the transceiver can configureitself as a hub transceiver by default. In some implementations, thetransceiver can configure itself as either a hub transceiver or a hubtransceiver, depending on its own configuration and the configuration ofthe hub transceiver that is transmitting the beacon message (e.g., asdescribe above).

Alternatively, if the transceiver does not receive any responses to thetransmitted message for a period of time (e.g., after a pre-determinedtime out period), the transceiver switches back to the receiver mode(block 2910). The transceiver can switch between the receiver mode andthe transmitter mode multiple times. (e.g., until it is assigned therole of a hub transceiver or the role of an edge transceiver, or until atime out period has elapsed and the process 2900 is restarted).

Referring back to block 2902, if the transceiver does not detect abeacon message during its initial laser scan, it can switch to thetransmitter mode (block 2910) and perform the operations describedabove.

In some implementations, one or more of the transceivers or transceivermodules described herein can be used to retrofit network devices toenhance the capabilities of those network devices. As an example,referring to FIG. 1 , one or more of the primary nodes 102 and thesecondary nodes 104 may be of a “legacy” design that does not supportone or more of the functions or operations described herein (e.g., adesign that was implemented prior to the general availability of the oneor more of the functions or operations). As another example, referringagain to FIG. 1 , one or more of the primary nodes 102 and the secondarynodes 104 may be devices that only support communications protocols thatare not directly compatible with those described herein. One or more ofthe transceivers or transceiver modules described herein can be coupledto these nodes to provide additional functionality to those nodes and/orto enable those nodes to communicate with other deices according to thecommunications protocols described herein. Accordingly, the networkdevices can be adapted for use on the optical communications network inan efficient and cost effective manner (e.g., without requiring that thenetwork devices be significantly modified or replaced). Further, thisenables the transceivers or transceivers to be replaced independent fromthe node.

FIG. 28A illustrates a state machine or flow diagram of phases forstarting-up a transceiver. In a first phase, 2802, the transceiver isplaced in an initialization state in which, for example, power issupplied to the transceiver. The transceiver may then enter into one ofphases 2804, 2806, 2808 for establishing two-way communication withanother transceiver in the network. In phase 2804, multiple transceiversmay be provided. The transceiver, therefore, scans the frequency oflight output from its local oscillator in order to detect a beacon fromthe other transceivers, referred to herein as a “peer-to-peer search.”The transceivers then exchange messages, as discussed above inconnection with FIGS. 22A-22C. Alternatively, in phase 2806, which maybe a “single carrier search,” only two transceivers are provided, andsuch transceivers exchange messages without carrying out the scan. Inphase 2808, the transceiver may begin transmitting and processingreceived optical subcarriers based on assignment information previouslystored in the transceiver (the “warmstart” phase). Typically, datastored in a memory, such an electrically erasable programmable read onlymemory (EEPROM), identifies which of phases 2804, 2806, and 2808 theedge node transceiver should enter.

After completion of one of phases 2804, 2806, and 2808, the edge nodetransceiver enters into a two-way communication phase with the hub node(phase 2810) based on amplitude modulation of optical subcarriersdiscussed above in connection with FIGS. 23A-23C. During phase 2810, thetransceiver will “negotiate” its role, e.g., whether the transceiver isto operate as an edge node or a hub node. Such negotiation is carriedout by exchanging message including information indicative of thecapacity, for example, of each transceiver. For example, if onetransceiver has a capacity of 400 Gbit/s and the other has a capacity of100 Gbit/s, the transceiver having the lower capacity will be designatedthe edge node and the higher capacity transceiver will be designated thehub node.

Following phase 2810, two optional phases are available, 2812 and 2814.Phase 2814 (“autonomous”) is carried out in the absence of centralsoftware, wherein allocation and bandwidth and/or assignment of opticalsubcarriers is carried out by the hub and edge nodes. Assignment of huband edge node roles may also be determined by the hub and edge nodes.Alternatively, when central software is present, such functions arecarried by the central software and instructions are provided to thetransceivers by way of the optical gateway, as discussed above, orthrough connections to the nodes housing the transceivers (phase2812—“Central Software”).

After transceiver roles and bandwidth has been allocated and/or opticalsubcarriers have been assigned to the edge nodes, the network is readyto begin operation including transmission of subcarriers carryinginformation indicative of user data (phase 2816).

FIG. 28B illustrates an alternative state machine or process flow 2850including phases for starting-up a transceiver in which in which centralsoftware communicates with transceivers without an initial“peer-to-peer” search (phase 2804) or a “single carrier search” (phase2806) described above. In a first phase, 2802, the transceiver is placedin an initialization state, as described above. The transceiver may thenenter into the “warmstart phase” (phase 2808), as further describedabove, or enter into two-way communication with the gateway (phase2852). For example, as noted above with respect to FIG. 26 , a laser2638 is optionally provided in gateway 2600. If gateway 2600 is providedcloser to the hub than the edge nodes, the laser may be provided as asource of light instead of one or more leaf lasers. As further shown inFIG. 26 and described above, such light from laser 2638 may bemodulated, after passing through combiner 2460, by VOA 2608, which maybe a fast VOA amplitude modulating (AM) such light based on an output ofDAC 2606 at the frequencies noted above with respect to FIGS. 23A-23C.Accordingly, DAC 2606, in this example, provides such AM modulationindicative of a beacon message similar to that described above. Thebeacon message is based on outputs of microprocessor 2602, which aresupplied to line system data generator 2604, which, based on suchreceived signals, provides additional signals to DAC 2606 for drivingVOA 2608. The outputs from microprocessor 2602 are based on instructionsor information provided by central software 111 via Ethernet port 2612.Thus, based on such instructions or information, the central softwarecan communicate with the transceiver by way of the above-described AMmodulation of the light provided by laser 2638.

In another example, central software 111 may communicate with thetransceiver through a host or node in which the transceiver is provided.Such communication may be by way of a virtual local area network (VLAN)providing Layer 2 (L2) management. As such, the transceiver may be ableto send and receive messages based on instructions/data from centralsoftware 111 via related information provided by the host or node to thetransceiver. In some implementations, central software 111 may provideinstructions for assigning hub and edge node roles to the transceiversin the network. Such roles may be tentative, however, and can bechanged.

After completion of phase 2852, transceivers may communicate with oneanother and the gateway (phase 2856) by way of the amplitude modulationsdescribed above. Since, at this point, the transceivers in the networkhave been activated and are communicating with one another, laser 2638,in one example, is no longer required to provide an optical output andmay be deactivated. In phase 2856, hub and leaf roles may be assignedbased on respective capacities of each transceiver.

Following phase 2852, either phase 2512 or phase 2514, as describedabove, may be entered into by the transceivers, after which thetransceivers are available for exchange information associated with userdata (phase 2816).

In some implementations, one or more of the transceivers or transceivermodules described herein can be physically coupled to a correspondingnetwork device, and once coupled, provide the network device withenhanced capabilities. For example, each transceiver or transceivermodule can include a physical communications interface (e.g., a plug orsocket having one or more electrical conduits for transmitting and/orreceiving electronic information) that can be inserted into acorresponding physical communication interface of a node (e.g., acorresponding socket or plug having one or more electrical conduits fortransmitting and/or receiving electronic information). In someimplementations, the transceiver or transceiver module may be referredto as a “pluggable” device or a “field replaceable unit (FRU)”.

FIGS. 30A and 30B show an example of a pluggable device 3000 that can beconfigured to perform one or more of the operations described herein.FIG. 30A shows the pluggable device 3000 according to a cross-sectionalside view, and FIG. 30B shows the pluggable device according to a topview.

As shown in FIGS. 30A and 30B, the pluggable device 3000 includes afirst physical communications interface 3002 (e.g., a plug having one ormore electrical conduits for transmitting and/or receiving electronicinformation) that is configured to couple with a corresponding physicalcommunications interface of another device (e.g., a corresponding socketconfigured to receive the plug and form one or more electricalconnections between the pluggable device 3000 and the other device). Insome implementations, the pluggable device 3000 can be (or can include)a transceiver, as described herein (e.g., a primary or hub transceiver,or a secondary or edge transceiver). In some implementations, the otherdevice can be a node, as described herein (e.g., a primary or nude nodeor a secondary or edge node).

Further, as shown in FIGS. 30A and 30B, the pluggable device 3000includes a second physical communications interface 3004 (e.g., a sockethaving one or more electrical conduits for transmitting and/or receivingelectronic information) that is configured to couple with acorresponding physical communications interface of a fiber optic cable3006 (e.g., having a corresponding plug configured to insert into thesocket and form one or more electrical connections between the pluggabledevice 3000 and the fiber optic cable 3006). In some implementations,the fiber optic cable 3006 can extend between the pluggable device 3000and the fiber plant of an optical communications network. For example,the fiber optic cable 3006 can communicatively couple the pluggabledevice 3000 and an OGW.

Further, as shown in FIGS. 30A and 30B, the pluggable device 3000includes a housing 3010. The housing 3010 can contain one or more of thecomponents described herein (e.g., as described with respect to FIGS.1B, 4A, 4B, 5, 6A-6C, 8, 9A-9C, 13-16, 19, and 20 .

Once the pluggable device 3000 and a node are coupled together, thepluggable device 3000 can receive information from the node via thephysical communications interface 3002 (e.g., information to betransmitted to the optical communications network), process theinformation such that it is suitable for transmission to the opticalcommunications network (e.g., using one or more of the techniquesdescribed herein to establish one or more communications channels, andto encode the information for transmission), and transmit theinformation to the optical communications network via the physicalcommunications interface 3004. Further, the pluggable device 3000 canreceive information from the optical communications network that is tobe delivered to the node via the physical communications interface 3004,process the information such that it is suitable for transmission to thenode, and transmit the information to the node via the physicalcommunications interface 30002.

In some implementations, one or more of the techniques described hereincan be performed by the transceiver using the optical communicationsnetwork, independent from the node. For example, in someimplementations, the transceivers can automatically establishcommunications channels with one another, automatically discoverinterconnections between one another and other network devices,automatically identify and correct misconfigurations, automaticallyoptimize their performance, automatically forward data between oneanother and other network devices, and/or automatically perform anyother operation on the optical communication network. Further, theseoperations can be performed without requiring input, instructions, orconfiguration information from the nodes. Accordingly, the transceivercan be used to enable various operations to be performed on the opticalcommunications network, even if the nodes were not originally designedto do so.

IV. Example Techniques for Regulating the Power of Signals on an OpticalCommunications Network

As discussed above (e.g., with respect to FIGS. 1, 2A-2C, 7, and 18 ),an optical communications network can include one or more opticalgateways (OGWs) to route data between transceivers. In someimplementations, an optical gateway can control the power of signalsthat are routed through the optical gateway (e.g., by selectivelyattenuating a subset of the signals) in order to balance the power ofsignals that are delivered to other devices on the opticalcommunications network. As can example, an optical gateway that controlthe power of signals that pass through it, such that the power of eachof the signals that are delivered to a transceiver (e.g., a hubtransceiver or an edge transceiver) are equal or approximately equal atthe point of delivery. This can be beneficial, for example, in improvingnetwork devices' compatibility with the optical communications networkor increasing the robustness of the optical communications networkagainst interference.

To illustrate, another example optical gateway 2600 is shown in FIG. 26. In general, the optical gateway 2600 can be similar to the line systemcomponent shown in FIG. 17 .

For example, as shown in FIG. 26 , optical gateway 2600 generallyincludes a DSP or microprocessor 2602, a line system data generator2604, a DAC 2606, one or more variable optical attenuators 2608 and2636, a laser control module 2610 for controlling a tunable laser 2638,an Ethernet module 2612, and an optical subcarrier power balancingmodule 2614. In some implementations, one or more of the components ofthe optical gateway 2600 can be placed at various locations along anoptical communication path of the system 100 (e.g., between one or morehub transceivers 106 and edge transceivers 108). In someimplementations, one or more of the components of the optical gateway2600 can be placed adjacent to a splitter/combiner (e.g., the splitter2642 and/or the combiner 2616 shown in FIG. 26 ) or in between twodistinct splitters that are each intermediate a hub transceiver 106 anda secondary transceiver 108. The optical gateway 2600 may also beprovided adjacent an optical amplifier.

In some implementations, control information can be provided to theoptical gateway 2600 based on the status of the line system component orother information associated with the line system component. Suchinformation may include operations, administration, maintenance, andprovisioning (OAM&P) information, such as, if the optical gateway 2600is adjacent an optical amplifier, the gain of the amplifier or whichoptical signals (by wavelength) are input to the amplifier.Alternatively, the control information may include an indication ofwhich optical signals and subcarriers are input to/output from specifiedports of the optical gateway. Such information may be supplied tocircuitry in the microprocessor or microcontroller 2602 referred to as aline system data generator 2604, which control data that is to betransmitted to a near end transceiver (e.g., a hub transceiver 106 oredge transceiver 108) of the system 100. The line system generator mayprovide the control data based on measured parameters associated withthe optical communication path or fiber links 2618 and/or 2620, forexample. For example, as noted above with respect to FIG. 7 , opticaltaps, such as tap 711 provide a portion of a transmitted optical signalincluding optical subcarriers to block 702 for determining such controlinformation. Alternatively, control information may be supplied to theline system generator 2604 by the central software 111 (e.g., via theEthernet module 2612, which includes one or more transceivers fortransmitting and receiving data via an Ethernet network). In a furtherexample, control information may be supplied directly from the centralsoftware 111 to the DAC 2606.

In some implementations, the line system data generator 2604 may supplythe control information as a digital or binary electrical signal to theDAC 206, which converts the received signal to an analog signalindicative of the control information to be transmitted. The analogsignal is then provided to the VOA 2608, for example via an opticalinput port 2622 a (e.g., an interface for receiving optical signals).The VOA 2608 may also receive an optical signal including a plurality ofoptical subcarriers (e.g., optical subcarriers SC1′ to SC16′, eachhaving a corresponding one of the frequencies f1′ to f16′) via anoptical input port 2622 b. In this example, the optical subcarriers SC1′to SC16′ are transmitted from one or more far end transceivers (e.g.,hub transceivers 106 and/or edge transceivers 108) on an optical fiberor optical communication path 2618. Based on the analog signal receivedvia the input port 2622 a, the VOA 2608 collectively adjusts theattenuation, and thus the amplitude or intensity, of optical subcarriersSC1′ to SC16′ based on the control information. As a result, the opticalsubcarriers SC1′ to SC16′ are amplitude modulated to carry such controlinformation to one or more near end primary transceivers 102 or edgetransceivers 104. Further, the optical subcarriers SC1′ to SC16′ can besplit (e.g., by the splitter 2642) and transmitted to one or more nearend transceivers (e.g., one or more hub transceivers 106 and/or edgetransceivers 108). In the example shown in FIG. 26 , the opticalsubcarriers SC1′ to SC8′ can be split and transmitted to 16 near endtransceivers.

In some implementations, control information can be transmitted to oneor more near end transceivers by injecting additional optical signalsusing a tunable laser 2638 and an optical tap 2640. For example, themicroprocessor 2602 can encode the control information (e.g., using oneor more modulation techniques) and control the VOA 2608 to generatepatterns of optical signals representative of the encoded controlinformation. These optical signals can be combined with the opticalsignals received from the far end transceivers, and transmitted to oneor more near end transceivers. As another example, the microprocessor2602 can instruct the laser control module 2610 to activate the tunablelaser 2638 and transmit signal according to a particular transmit power(e.g., to supply an optical signal to the VOA 2608, such as when no farend transceivers are transmitting any optical signals).

In some implementations, the optical gateway 2600 also can detectoptical signals including amplitude modulated subcarriers transmitted onan optical communication path 2620 from one or more near endtransceivers (e.g., one or more hub transceivers 106 or edgetransceivers 108), such as the optical subcarriers SC1 to SC16. Theoptical signals are input to optical taps 2620, which may provideoptical power split portion of the optical signal (e.g., 1% to 10%) torespective photodiode circuits 2626. A remaining portion of the opticalsignal continues to propagate along optical communication path 2620.VOAs 2636 optionally may be provided for power balancing. For example,VOAs 2636 can receive the signal output by the optical taps 2624 viaoptical input ports 2628 a, and attenuate the signal according to ananalog signal 2630 received via optical input ports 2630 b (e.g.,control information received from one or more sources, such as thesubcarrier power balancing module 2614).

In some implementations, the VOA 2608 can have greater capabilities thanthe VOAs 2636. For example, in some implementations, the VOA 2608 can beconfigured to switch between different levels of attenuation relativelyrapidly (e.g., to provide amplitude modulated signals). In contrast, theVOAs 2636 can be configured to switch between different levels ofattenuation relatively slowly (e.g., to provide power balancing, whichmay not require as rapid of shifting). Nevertheless, in someimplementations, the VOAs 2608 and 2636 can be similar or identical.

As further shown in FIG. 26 , the tapped portion of the optical signalis converted by the photodiode circuit 2626 to a corresponding analogelectrical signal (e.g., a voltage or a current). The analog signal isfed to an analog-to-digital conversion circuit 2630, which suppliesdigital signals based on the received analog signal. Such digitalsignals are optionally provided to a filter 2632 (e.g., a low passfilter or band pass filter) and then output to a conventional clock anddata recovery circuitry 2634, which outputs the control information tothe central software 111, for example by way of an optical signal (e.g.,an optical service channel (OSC)), or by way of an electrical signal(e.g., an Ethernet signal generated by the Ethernet module 2612).

As shown in FIG. 26 , in some cases, the optical gateway 2600 canreceive and process multiple optical subcarriers concurrently (e.g., theoptical subcarriers SC1 to SC16) using an array of optical taps 2624,VOAs 2636, photodiode circuits 2626, ADCs 2630, filters 2632, CDRs,and/or clock and data recovery circuitry 2634. Further, multiple opticalsubcarriers (e.g., the optical subcarriers SC1 to SC16) can be combined(e.g., by the combiner 2616) and transmitted to the line system forrouting to one or more far end transceivers (e.g., one or more hubtransceivers 106 and/or edge transceivers 108). In the example shown inFIG. 26 , sixteen optical subcarriers are processed (e.g., by an arrayof sixteen sets of the components described above), and combined andtransmitted to the line system.

In some implementations, a parameter associated with line systemcomponent may be adjusted or controlled based on the received controlinformation. For example, if the line system component includes anoptical amplifier, such as an erbium doped fiber amplifier, the controlinformation may include instructions or other data for adjusting a gainof the optical amplifier. Alternatively, or in addition, the controlinformation may include information for adjusting an attenuation of theVOAs 2636.

As described herein, in some implementations, the optical gateway 2600also can control the power of signals that are routed through theoptical gateway 2600 (e.g., by selectively attenuating a subset of thesignals) in order to balance the power of signals that are delivered toother devices on the optical communications network (e.g., far endtransceivers, such as hub transceivers 106 or edge transceivers 108)and/or to improve the quality (e.g., increase the signal to noise ratio)of those signals). As an example, an optical gateway can control thepower of signals that pass through it, such that the power of each ofthe signals that are delivered to a transceiver (e.g., a hubtransceiver) are equal or approximately equal at the point of delivery.As another example, the optical gateway can control the power of signalsthat pass through it, such that the power of each of the signals thatare delivered to a transceiver (e.g., a hub transceiver or an edgetransceiver) do not deviate from one another by more than a particularthreshold amount (e.g., an empirically determined value). As anotherexample, the optical gateway can control the power of signals that passthrough it, such that the signal to noise ratio of the signals that aredelivered to a transceiver (e.g., a hub transceiver or an edgetransceiver) are greater than a minimal threshold level (e.g., anempirically determined value).

As an example, the optical gateway 2600 can measure the properties ofoptical signals received from each of the optical taps 2624 (e.g.,power) using the photodetector circuits 2626, and provide themeasurements to the subcarrier power balancing module 2614. Thesubcarrier power balancing module 2614 can determine whether the powerof those signals should be adjusted, and if so, instruct the VOAs 2636to attenuate one or more of the optical signals selectively. Forexample, if subcarrier power balancing 2614 determines that the power ofa particular optical signal should be reduced, the subcarrier powerbalancing module 2614 can selectively instruct the corresponding VOA2636 to attenuate that signal. Further, the subcarrier power balancingmodule 2614 can continue receiving measurements from the photodetectorcircuits 2626 and adjusting the attenuation provided by the VOAs 2636over time (e.g., as a control loop).

In some implementations, the subcarrier power balancing module 2614 candetermine whether the power of any of the signals should be adjustedbased on information received from one of the transceivers. For example,the subcarrier power balancing module 2614 can receive, from each of thedestination transceivers, measurement data regarding the signalsreceived by that transceiver (e.g., power, signal to noise ratio, etc.).In some implementations, if the power of a particular received signalexceeds the power of other received signals, the subcarrier powerbalancing module 2614 can selectively attenuate the higher poweredsignal using the corresponding VOA (e.g., to “balance” the powers of thesignals received by the transceiver). In some implementations, if thesignal to noise ratio of a particular received signal is less than aminimal threshold value, the subcarrier power balancing module 2614 canmodify an attenuation of a signal (or stop attenuating the signalaltogether) using the corresponding VOA (e.g., to increase the signal tonoise ratio).

In some implementations, the measurement data can be received from thecentral software 111 and/or from one or more of the transceiversdirectly (e.g., using one or more of the control channels describedherein, for example with respect to FIGS. 2A-2C).

In some implementations, the optical gateway 2600 also can selectivelyprevent one of more of the signals that it receives from being routed toanother device. This feature can be useful, for example, if the opticalgateway 2600 receives signals from a malfunctioning or erranttransceiver (e.g., signals that do not conform with the communicationsprotocols of the optical communications network). In someimplementations, this feature can be performed by attenuating theoptical signal selectively using one or more of the VOAs 2636 to blockthe signals from propagating through the optical gateway 2600. The VOAs2636 can be controlled, for example, by the subcarrier power balancingmodule 2614 and/or the microprocessor 2602 based on measurementsobtained by the photodiode circuits 2626.

In some implementations, power balancing can be performed by one or moreof the transceivers themselves, independent of an optical gateway. Thiscan be useful, for example, as it enables the transceivers to adjusttheir configuration automatically, with or without input from otherdevices.

For instance, a first transceiver (e.g., a hub transceiver 106 or anedge transceiver 108) can transmit signals to a second transceiver(e.g., hub transceiver 106 or an edge transceiver 108). Further, thefirst transceiver can receive measurement data from the secondtransceiver regarding the signal that was received from the firsttransceiver (e.g., measurements regarding one or more “quality metrics”that describe the properties of the signal, such as power, signal tonoise ratio, etc.), as well as measurement data regarding one or moreother signals received from one or more other transceivers (e.g.,measurement regarding one more quality metrics, such as power, signal tonoise ratio, etc.). In some implementations, if the power of the signalthat was received by the second transceiver from the first transceiverdeviates from the powers of the signals that were received by the secondtransceiver from the other transceivers, the first transceiver canadjust the transmit power of its signal to reduce or eliminate thedeviation (e.g., to “balance” the powers of the signals received by thesecond transceiver). In some implementations, if the signal to noiseratio of a particular received signal is less than a minimal thresholdvalue, the first transceiver can change its transmit power of its signal(e.g., to increase the signal to noise ratio).

As an example, if the power of the signal that is received by the secondtransceiver from the first transceiver is higher than the powers of thesignals that are received by the second transceiver from the othertransceivers, the first transceiver can decrease the power by which thesignal is transmitted to the second transceiver (e.g., by reducing thepower of a signal amplifier and/or reducing the power of a laser). Asanother example, if the power of the signal that is received by thesecond transceiver from the first transceiver is lower than the powersof the signals that are received by the second transceiver from theother transceivers, the first transceiver can increase the power bywhich the signal is transmitted to the second transceiver (e.g., byincreasing the power of a signal amplifier and/or increasing the powerof a laser). As another example, if the signal to noise ratio of thesignal that is received by the second transceiver from the firsttransceiver is lower than a minimum threshold value, the firsttransceiver can modify the power by which the signal is transmitted tothe second transceiver (e.g., by modifying the power of a signalamplifier and/or modifying the power of a laser).

In some implementations, a transceiver can receive measurement data fromthe central software 111 and/or from one or more of the transceiversdirectly (e.g., using one or more of the control channels describedherein, for example with respect to FIGS. 2A-2C).

The power balancing techniques described herein can provide varioustechnical benefits. For example, FIG. 27 shows an example networktopography 2700 of an optical communications network interconnecting afirst transceiver 2702 a and a second transceiver 2702 b (e.g., edgetransceivers) to a third transceiver 2702 c (e.g., a hub transceiver).Each of the edge and hub transceivers can be implemented, for example,as described above. As shown in FIG. 27 , the first transceiver 2702 aand the second transceiver 2702 b are communicatively coupled to apassive splitter 2704, which in turn is communicatively coupled to anamplified ring 2706 having multiple reconfigurable optical add-dropmultiplexers (ROADMs) 2708. The third transceiver 2704 b iscommunicatively coupled to one of the ROADMs 2708 of the amplified ring2706. Due to the difference between (i) the signal path from the firsttransceiver 2702 a to the third transceiver 2702 c, and (ii) the signalpath from the second transceiver 2702 b to the third transceiver 2702 c,signals transmitted by the first transceiver 2702 a and the secondtransceiver 2702 a will experience different degrees of attenuation asthey travel to the third transceiver 2702 c. Accordingly, the signals(e.g., corresponding to different optical subcarriers) may differ inpower and/or signal to noise ratio upon delivery to the thirdtransceiver 2702 c. As described herein, the first transceiver 2702 aand/or the second transceiver 2702 b can receive measurement data fromthe third transceiver 2702 c regarding the power of signals received bythe third transceiver 2702 c, and selectively control their transmissionpower to “balance” the power of signals received by the thirdtransceiver 2702 c (e.g., to reduce or eliminate a deviation in thepowers of the received signals) and/or to improve of those signals.

Although the disclosure herein primarily discusses the assignment orallotment of digital subcarriers (and corresponding frequencies offrequency ranges) to transceivers for communication on an opticalcommunication network), in some implementations, other network resourcecan also be assigned or allotted to transceivers for such communication,either instead of or in addition to those above. For example, in someimplementations, a hub transceiver can assign or allot one or more timeslots or ranges of time slots for edge transceivers to transmit and/orreceive data on the optical communications network. This can bebeneficial, for example, as it enables multiple edge transceivers totransmit and/or receive data using a common set of certain networkresources (e.g., digital subcarriers, frequencies, etc.), but accordingto different times such that no two communications overlap in time andpotentially interfere with one another (e.g., such that there is no“collision” between the communications).

As an example FIG. 35 shows several example time slots 3500 a-3500 e. Ahub transceiver can assign or allot one or more of these time slots toeach edge transceiver, and transmit an indication of the assigned orallotted time slot(s) to each transceiver. In turn, each transceiver cantransmit and/or receive data from the optical communications networkaccording to the assigned time slot(s). In some implementations, thetime slots that are assigned or allotted to each edge transceiver canrepeat in time (e.g., according to a periodic pattern, or some otherpattern).

V. Example Control Data and Telemetry Data

As described herein, in some implementations, the devices of an opticalcommunications network can transmit control data and/or telemetry datato one or more other devices of the optical communications network byway of, for example, the amplitude modulation techniques and associatedcircuitry described above. As an example, a device can transmit, to oneor more other devices, control data to instruct the other devices toperform certain actions, to modify the operation of the other devices,etc. As another example, a device can transmit, to one or more otherdevices, telemetry data regarding operations performed by one or moredevices of the optical communications network and/or the status of theone or more devices.

In some implementations, a first transceiver (e.g., a hub transceiver oran edge transceiver) can transmit control data and/or telemetry data toa second transceiver (e.g., a hub transceiver or an edge transceiver) tocontrol the operation of the second transceiver and/or to provideinformation to the second transceiver (e.g., regarding operationsperformed by the first transceiver or the status of the firsttransceiver). In some implementations, the control data and/or telemetrydata can be transmitted between the devices using one or more of thecontrol channels described herein, for example with respect to FIGS.2A-2C.

Further, in some implementations, at least some of the control dataand/or the telemetry data can be transmitted independent of the centralsoftware 111. For example, one transceiver can transmit information toanother transceiver directly, without relying on the central software111. This feature can be beneficial, for example, as it can enabletransceivers to communicate with one another to coordinate theiroperations with respect to an optical communications networkautomatically.

In some implementations, a first transceiver (e.g., an edge transceiver)can transmit control data to a second transceiver (e.g., a hubtransceiver) requesting that the first transceiver be allotted one ormore optical subcarriers for use on the optical communications network.In response, the second transceiver to either allot the one or morerequested optical subcarriers to the first transceiver (e.g., if the oneor more requested optical subcarriers are available for allotment). Anexample of this control data is described, for example, with respect toFIG. 21 .

In some implementations, a first transceiver (e.g., a hub transceiver)can transmit control data to a second transceiver (e.g., an edgetransceiver) requesting that the second transceiver release orrelinquish an optical subcarrier that had been previously allotted tothe second transceiver. In response, the second transceiver can refrainfrom using the optical subcarrier with respect to the opticalcommunications network.

In some implementations, a first transceiver (e.g., a hub transceiver)can transmit control data to a second transceiver (e.g., an edgetransceiver) requesting that the second transceiver turn on or off anidle optical subcarrier (e.g., as described with respect to FIG. 24 ).In response, the second transceiver can turn on or off the idle opticalsubcarrier.

In some implementations, a first transceiver (e.g., a hub transceiver)can transmit control data to a second transceiver (e.g., an edgetransceiver) requesting that the second transceiver disconnect from theoptical communications network. In response, the second transceiver canrelinquish any optical subcarriers that had been allotted to it for useon the optical communications network, and disconnect from the opticalcommunications network.

In some implementations, a first transceiver (e.g., a hub transceiver oran edge transceiver) can transmit control data to a second transceiver(e.g., a hub transceiver or an edge transceiver) requesting that thesecond transceiver perform an optical spectral analysis or scan of itsreceived signals in a manner similar to that described (e.g., asdescribed with respect to FIGS. 22A-22C). The request can specify theparameters of the analysis (e.g., the range of frequencies that shouldbe analyzed, the resolution of the analysis, the time during which theanalysis should be conducted, the type of analysis that should beperformed, the frequency bins that should be used for the analysis,etc.). In response, the second transceiver can perform the requestedanalysis, and transmit the results of the analysis to the firsttransceiver.

In some implementations, a first transceiver (e.g., a hub transceiver oran edge transceiver) can transmit control data to a second transceiver(e.g., a hub transceiver or an edge transceiver) requesting that thesecond transceiver upgrade or modify its firmware or software. In someimplementations, the control data can include a copy of the upgradedfirmware or software, or identify a network location from which theupgraded firmware or software can be retrieved. In response, the secondtransceiver can upgrade its firmware or software according to therequest.

In some implementations, a first transceiver (e.g., a hub transceiver oran edge transceiver) can transmit control data to a second transceiver(e.g., a hub transceiver or an edge transceiver) requesting that thesecond transceiver forwarded particular data to a third transceiver(e.g., a hub transceiver or an edge transceiver). In response, thesecond transceiver can forward the identified data to the thirdtransceiver. This can be useful, for example, as it may enable data tobe transmitted between transceivers through one or more intermediaries,even if a direct network link is not available those transceivers.

In some implementations, a first transceiver (e.g., a hub transceiver oran edge transceiver) can transmit control data to a second transceiver(e.g., a hub transceiver or an edge transceiver) requesting that thesecond transceiver transmit telemetry data to the first transceiver. Inresponse, the second transceiver can transmit the requested telemetrydata to the first transceiver.

In some implementations, telemetry data can include informationregarding the identity of the second transceiver. As an example,telemetry data can include information regarding the current status ofthe second transceiver (e.g., optical launch power, processorutilization, memory utilization, bandwidth utilization, other resourceutilization, power state, temperature, etc.). As another example,telemetry data can include information a transmission of signals by thesecond transceiver (e.g., the transmit power, the optical subcarriersassigned to the second transceiver for data transmission and allottedfor reception, the modulation schemes, such as BPSK, QPSK, and m-QAM,where M is a positive integer greater than 4) used to encode thetransmitted data, or any other information regarding the transmission ofdata by the second transceiver). As another example, telemetry data caninclude information a receipt of signals by the second transceiver(e.g., the power of the received signals, the optical signal to noiseratio (OSNR) of the received signals, the optical subcarriers allottedto the second transceiver for data reception, the modulation schemesused to decode the received data, or any other information regarding thereceipt of data by the second transceiver). As another example,telemetry data can include any other information regarding the secondtransceiver or operations performed by the second transceiver (e.g.,information regarding any of the operations described herein).

FIG. 31A shows an example process 3100 that can be performed using oneor more of the systems described herein. For instance, the process 3100can be performed using an optical communication system including one ormore of the components one or more hub transceivers and edgetransceivers (e.g., as shown in FIGS. 1, 2A-2C, and 18 ).

According to the process 3100, a control module is communicativelycoupled to an optical communications network (e.g., via one or moreoptical links, electrical links, wireless communications links, etc.).The control module receives, from one or more edge transceivers or hubtransceiver of the optical communications network, telemetry dataregarding at least one of a transmission or a receipt of data over theoptical communications network (block 3102). As an example, an edgetransceiver could be a secondary transceiver or edge transceiver 104, asdescribed above. As another example, a hub transceiver could be aprimary transceiver or hub transceiver 106, as described above.

In some implementations, the control module can be remote from the hubtransceiver and the plurality of edge transceivers. For example, thecontrol module can be implemented as a part of the central software 111,or as another component of the optical communications network. In someimplementations, the control module can be included in one of the edgetransceivers or the hub transceiver. In some implementations, thecontrol module can be included in a node (e.g., a computer system) thatis physically coupled to one of the edge transceivers or the hubtransceiver (e.g., via a physical communications interface, such as aplug or socket, for instance as shown in FIG. 30 ).

In some implementations, the telemetry data can be received by thecontrol module periodically, continuously, and/or intermittently.

The control module determines, based on the telemetry data, performancecharacteristics regarding the optical communications network (block3104).

The control module transmits, based on the performance characteristics,a command to one or more of the edge transceivers or the hub transceiverto modify an operation with respect to the optical communicationsnetwork (step block 3106).

The telemetry data and the command can be interrelated. As an example,the telemetry data can include an indication of a respective transmitpower of one or more of the edge transceivers or the hub transceiver.Correspondingly, the command can include an indication to modify arespective transmit power of one or more of the edge transceivers or thehub transceiver.

As another example, the telemetry data can include an indication of arespective subset of network resources of the optical communicationsnetwork assigned to one or more of the edge transceivers or the hubtransceiver for use in communicating over the optical communicationsnetwork. For instance, the network sources can be a particular bandwidthor range of bandwidths, frequencies or range of frequencies, opticalsubcarriers or range of optical subcarriers, time slots or range of timeslots, and/or any other network resource that is used to communicate onthe optical communications network. Correspondingly, the command caninclude an assignment of a different subset of network resources of theoptical communications network to one or more of the edge transceiversor the hub transceiver for use in communicating over the opticalcommunications network.

As another example, the telemetry data can include a temperature of afirst edge communications of the plurality of edge transceivers.Correspondingly, the command can include an indication to modify a powerprovided to the first edge transceiver based on the temperature of thefirst edge transceiver. In some implementations, the command can includean indication to modify a power provided to one or more second edgetransceiver of the plurality of edge transceiver based on thetemperature of the first edge transceiver.

Additional examples of telemetry data and commands are described above.

VI. Example Discovery of Misconfigurations with Respect to the OpticalCommunications Network

As described herein, in some implementations, the devices of an opticalcommunications network can automatically detect misconfigurations withrespect to the optical communication network, and automatically correctthose misconfigurations. In some implementations, the detection andcorrection of misconfiguration can be performed independent of thecentral software 111. This can be beneficial, for example, as it mayenable transceivers to adjust their configurations autonomously, suchthat communications on the optical communications network are notdisrupted.

In some implementations, a first hub transceiver can determine that itand a second hub transceiver have been assigned respective sets ofoptical subcarriers (e.g., for allotment to their respective edgetransceivers) that overlap or “collide” with one another. Due to thisoverlapping or colliding assignment, the hub transceivers may raise analarm condition that the one or more of the same optical subcarriershave been allocated to two different hub transceivers, and would resultin collisions or signal interference. The assignments can then bereviewed, and a new allocation of optical subcarriers can be provided tothe hub transceivers without network disruption of the traffic that thefirst hub or the second hub are serving.

To detect this condition, the first hub transceiver can identify thesets of optical subcarriers that are assigned to the second hubtransceiver by monitoring the optical network for messages transmittedfrom one or more edge transceivers and intended for the second hubtransceiver. These edge messages may include an indication of the setsof optical subcarriers that are assigned to the second hub transceiver.For example, the message can include a copy or “echo” of the beaconmessage that is transmitted by the second hub transceiver to each of itsedge transceivers, which includes a list of each of the opticalsubcarriers that are currently assigned to the hub transceiver and madeavailable for allotment.

In some implementations, a first transceiver (e.g., a hub transceiver oran edge transceiver) and a second transceiver (e.g., a hub transceiveror an edge transceiver) are communicating to an optical gateway usingoverlapping or colliding communication channels (e.g., via overlappingfrequencies or frequency bands). Due to these overlapping or collidingcommunications channels, the communications between the transceiver andthe optical gateway may be misrouted or experience signal interference.

To correct this misconfiguration, upon detecting this overlap orcollision, the optical gateway can request that the first transceiveruse a different frequency or frequency band to communicate with theoptical gateway (e.g., such that there is no longer an overlap orcollision).

FIG. 31B shows an example process 3110 that can be performed using oneor more of the systems described herein. For instance, the process 3110can be performed using an optical communication system including one ormore of the components one or more hub transceivers and edgetransceivers (e.g., as shown in FIGS. 1, 2A-2C, and 18 ).

According to the process 3110, a first hub transceiver communicativelycoupled to an optical communications network (e.g., via one or moreoptical links, electrical links, etc.). The first hub transceiverdetermines that the first hub transceiver is configured to assign afirst subset of network resources of the optical communications networkto a first subset of the edge transceivers for communication over theoptical communications network (block 3112). As an example, each of thehub transceiver could be a primary transceiver or hub transceiver 106,as described above

The first hub transceiver determines that a second hub transceiver isconfigured to assign a second subset of network resources of the opticalcommunications network to a second subset of the edge transceivers forcommunication over the optical communications network (block 3114).

The first hub transceiver determines that the first subset of networkresources overlaps the second subset of network resources (step 3116).

In some implementations, the network resources can include a particularbandwidth or range of bandwidths, frequencies or range of frequencies,optical subcarriers or range of optical subcarriers, time slots or rangeof time slots, and/or any other network resource that is used tocommunicate on the optical communications network.

In some implementations, the first subset of network resources caninclude a first frequency band, and the second subset of networkresources can include a second frequency band. Determining that thefirst subset of network resources overlaps the second subset of networkresources can include determining that the first frequency band overlapsthe second frequency band overlap.

In some implementations, the first subset of network resources caninclude one or more first time slots for communicating over the opticalcommunications network, and the second subset of network resources caninclude one or more second time slots for communicating over the opticalcommunications networks. Determining that the first subset of networkresources overlaps the second subset of network resources can includedetermining that the one or more first time slots overlap the one moresecond time slots.

In response to determining that the first subset of network resourcesoverlaps the second subset of network resources, the first hubtransceiver transmits a notification of the overlap to a control moduleof the optical communications network (step 3118).

In some implementations, the control module can be remote from the hubtransceivers. For example, the control module can be implemented as apart of the central software 111, or as another component of the opticalcommunications network. In some implementations, the control module canbe included in one of the hub transceivers. In some implementations, thecontrol module can be included in a node (e.g., a computer system) thatis physically coupled to one of the hub transceivers (e.g., via aphysical communications interface, such as a plug or socket, forinstance as shown in FIG. 30 ).

In some implementations, the process 3110 can also include, in responseto determining that the first subset of network resources overlaps thesecond subset of network resources, refraining from transmitting dataduring first subset of network resources by the first hub transceiver.

In some implementations, the first hub transceiver can determine thatthe second hub transceiver is configured to assign the second subset ofnetwork resources to the second subset of the edge transceivers based onmessages transmitted by one or more of the second subset of the edgetransceivers. For example, the first hub transceiver can receive one ormore messages transmitted by one or more of the second subset of theedge transceivers and intended for delivery to the second hubtransceiver, where the one or more messages include an indication of thesecond subset of network resources.

In some implementations, the first hub transceiver and/or the second hubtransceiver can include an external connection interface for coupling toa network node. For example, the first hub transceiver and/or the secondhub transceiver can include one or more of the physical communicationinterfaces shown and described with respect to FIG. 30 . In someimplementations, the network node can be a primary node or hub node 106.

VII. Example Discovery of Fiber Plant of the Optical CommunicationsNetwork

In some implementations, an optical gateway (e.g., the optical gatewaydescribed with respect to FIGS. 7 and 26 ) can be configured toautomatically determine the fiber topology or interconnections betweenit and the other devices of the optical communications network. As anexample, the optical gateway can determine, for each of its ports (e.g.,each of its physical interfaces for receiving a physical optical link,such as a fiber optical cable), the optical link that is coupled to thatport, and the one or more other devices that are coupled to that opticallink (e.g., one or more hub transceivers or edge transceivers). In someimplementations, the optical gateway can determine, for each port, theidentity of each of the transceivers that are coupled to that opticallink (e.g., unique identifiers that distinguish the transceivers fromother transceivers on the optical communications network).

This technique for “auto discovery” of interconnections on the opticalnetwork can provide various benefits. For example, this process mayenable an optical gateway to automatically ascertain the configurationof at least a portion the optical communications network. In someimplementation, this information can be provided to a user (e.g., to aidin the administration of the system, the identification andrectification of misconfigurations with respect to the system, theplanning of improvements or enhancements of the system, etc.). In someimplementation, this information can be provided to other devices of thesystem (e.g., to aid in the automatic configuration of the system, theautomatic identification and rectification of misconfigurations withrespect to the system, etc.).

FIG. 31C shows an example process 3120 that can be performed using oneor more of the systems described herein. For instance, the process 3120can be performed using an optical communication system including anoptical gateway (e.g., as shown in FIGS. 1, 2A-2C, 7, 18, and 26 ).

According to the process 3120, an optical gateway communicativelycoupled to an optical communications network (e.g., via one or moreoptical links, electrical links, etc.). As an example, the opticalgateway can be the OGW 103-1 or the OGW 103-2. The optical gatewayreceives a plurality of signals from the optical communications networkat a plurality of ports of the optical gateway (block 3122). Each portof the optical gateway includes one or more respective photodiodes(e.g., as shown in FIG. 7 ).

The optical gateway determines, for each port, (i) a respective link ofthe optical communications network communicatively coupling the portwith at least one hub transceiver communicatively coupled to the opticalcommunications network or with at least one edge transceivercommunicatively coupled to the optical communications network, and (ii)an identity of the at least one hub transceiver or the at least one edgetransceiver (block 3124). As an example, an edge transceiver could be asecond transceiver or edge transceiver 104, as described above. Asanother example, a hub transceiver could be a primary transceiver or hubtransceiver 106, as described above. In some implementation, each of thelinks can include one or more lengths of optical fiber.

In some implementations, according to the process 3120, the opticalgateway can receive a first signal of the plurality of signals from atleast one hub transceiver of a plurality of hub transceivers or from atleast one edge transceiver of a plurality of edge transceivers. Theoptical gateway can determine a power of the received first signal,attenuate the first signal based on the power of the received firstsignal (e.g., using one or more VOAs). Further, the optical gateway cantransmit the attenuated first signal to another transceiver of theoptical communications network.

In some implementations, the first signal can be attenuated furtherbased on one or more commands received from a control module of theoptical communications network. In some implementations, the controlmodule can be remote from the optical gateway and the transceivers. Forexample, the control module can be implemented as a part of the centralsoftware 111, or as another component of the optical communicationsnetwork. In some implementations, the control module can be included inone of the transceivers or the optical gateway. In some implementations,the control module can be included in a node (e.g., a computer system)that is physically coupled to one of the transceivers (e.g., via aphysical communications interface, such as a plug or socket, forinstance as shown in FIG. 30 ).

VIII. Other Example Processes for Performing the Techniques DescribedHerein

FIG. 31D shows an example process 3130 that can be performed using oneor more of the systems described herein. For instance, the process 3130can be performed using an optical communication system including aprimary transceiver and a plurality to secondary transceivers (e.g., asshown in FIGS. 1, 2A-2C, and 18 ).

According to the process 3130, an edge transceiver is communicativelycoupled to a first network node and to an optical communications network(e.g., via one or more optical links, electrical links, etc.). The edgetransceiver receives a first message from a hub transceiver over a firstcommunications channel of the optical communications network (block3132). The first message includes an indication of available networkresources on the optical communications network.

In some implementations, the network resources can include a particularbandwidth or range of bandwidths, frequencies or range of frequencies,optical subcarriers or range of optical subcarriers, time slots or rangeof time slots, and/or any other network resource that is used tocommunicate on the optical communications network.

In some implementations, the indication of the available networkresources on the optical communications network can include anindication of a plurality of optical subcarriers of the opticalcommunications network, and an identity (e.g., in index value, or someother identifier) of one or more of the optical subcarriers that are notcurrently assigned to the edge transceiver or any other edgetransceivers of the optical communications network.

In some implementations, the first communications channel can includefirst signals that have been amplitude modulated with respect to each ofthe plurality of optical subcarriers. In some implementations, thesecond communications channel can include second signals transmittedaccording to one or more frequencies that do not coincide with theplurality of optical subcarriers. In some implementations, at least oneof the first communications channel or the second communications channelcorresponds to a respective optical subcarrier. Examples of thesecommunications channels are described, for example, with respect toFIGS. 2A-2C, 21, and 23A-23C.

In some implementations, the first message can also include instructionsfor requesting assignment of the one or more of the optical subcarriersthat are not currently assigned to the edge transceiver or any otheredge transceivers of the optical communications network. Exampleinstructions are described, for example, with respect to FIG. 21 .

Additional details regarding the first message are described, forexample, with respect to FIG. 21 (e.g., block 2108).

In some implementations, the edge transceiver could be a secondarytransceiver or edge transceiver 104, as described above. In someimplementations, the hub transceiver could be a primary transceiver orhub transceiver 106, as described above. Further, the first network nodecan be a computer system that is physically coupled to the edgetransceiver (e.g., via a physical communications interface, such as aplug or socket, for instance as shown in FIG. 30 ).

The edge transceiver transmits, over a second communications channel ofthe optical communications network, a second message to the hubtransceiver (block 3134). The second message includes an indication of asubset of the available network resources selected by the edgetransceiver for use in communicating over the optical communicationsnetwork.

Additional details regarding the second message are described, forexample, with respect to FIG. 21 (e.g., block 2110).

The edge transceiver receives, from the hub transceiver, a third messageacknowledging receipt of a selection by the edge transceiver (block3136). Additional details regarding the third message are described, forexample, with respect to FIG. 21 (e.g., block 2112).

In some implementations, the edge transceiver can transmit the secondmessage to the hub transceiver periodically until the third message isreceived by the edge transceiver from the hub transceiver.

The edge transceiver receives, from the hub transceiver, a fourthmessage confirming an assignment of the selected subset of the availablenetwork resources to the edge transceiver for use in communicating overthe optical communications network (block 3138). Additional detailsregarding the fourth message are described, for example, with respect toFIG. 21 (e.g., block 2116).

The edge transceiver transmits, using the selected subset of theavailable network resources, data from the first network node to asecond network node via the hub transceiver (block 3140). As an example,the second network node can be another computer system on the opticalcommunications network.

In some implementations, the edge transmit can receive additionalmessages from the hub transceiver, and perform certain operations isresponse. As an example, the edge transceiver can receive a message fromthe hub transceiver including a command to modify an assignment ofnetwork resources to the edge transceiver. In response, the edgetransceiver can transmit data from the first network node to the secondnetwork node via the hub transceiver according to the modifiedassignment of network resources.

As another example, the edge transceiver can receive a message from thehub transceiver including a command to relinquish the subset of networkresources that had been assigned to the edge transceiver. In response,the edge transceiver can refrain from transmitting data to the hubtransceiver using the subset of network resources that had been assignedto the edge transceiver.

As another example, the edge transceiver can receive a message from thehub transceiver including a request for a status of the edgetransceiver. In response, the edge transceiver can transmit the statusof the edge transceiver to the hub transceiver. In some implementations,the edge transceiver can transmit the status of the edge transceiver tothe hub transceiver periodically (e.g., without the hub transceivermaking a request for it status).

As another example, the edge transceiver can receive a message from thehub transceiver including a command to modify a transmit power of theedge transceiver. In response, the edge transceiver can transmit datafrom the first network node to a second network node via the hubtransceiver according to the modified transmit power.

As another example, the edge transceiver can receive a message from thehub transceiver including a command to forward data from the edgetransceiver to a further transceiver communicatively coupled to theoptical communications network. In response, the edge transceiver canforward the data to the further transceiver according to the fifthmessage. In some implementations, the further transceiver can be anotheredge transceiver of the optical communications network.

In some implementations, according to the process 3130, the edgetransceiver can also determine a carrier frequency associated with thehub transceiver. To determine a carrier frequency associated with thehub transceiver, the edge receive can receive a signal from the hubtransceiver via the optical communications network (e.g., by scanning afrequency range using a local oscillator of the edge transceiver, wherethe frequency range including a plurality of frequency subsets).Further, the edge transceiver can determine a plurality of power valuesof the optical signal, each of the plurality of power values beingassociated with a corresponding one of the plurality of frequencysubsets. Further, the edge transceiver can determine, based on theplurality of power values, a carrier frequency associated with the hubtransceiver. In some implementations, the power level can correspond tothe carrier frequency is greater than the power values corresponding tothe frequency ranges that do not coincide with the carrier frequency.

Additional details regarding determining a carrier frequency aredescribed, for example, with respect to FIGS. 22A-22E.

In some implementations, according to the process 3130, the edgetransceiver can also receive, from the hub transceiver, one or morequality metrics regarding a signal transmitted from the edge transceiverto the hub transceiver. Further, the edge transceiver can modify one ormore control parameters for transmitting data based on the one or morequality metrics. In some implementations, the one or more controlparameters can include a transmit power of the first edge transceiver.As an example, the edge transceiver can perform a power balancingoperation according to the process described with respect to FIGS. 26and 27 .

FIG. 31E shows an example process 3150 that can be performed using oneor more of the systems described herein. For instance, the process 3150can be performed using an optical communication system including aprimary transceiver and a plurality to secondary transceivers (e.g., asshown in FIGS. 1, 2A-2C, and 18 ).

According to the process 3150, a hub transceiver communicatively coupledto a first network node and to an optical communications network. Thehub transceiver determines a plurality of optical subcarriers availablefor assignment by the hub transceiver to a plurality of edgetransceivers for use in communicating over the optical communicationsnetwork (block 3152). As an example, an edge transceiver could be asecondary transceiver or edge transceiver 104, as described above. Asanother example, a hub transceiver could be a primary transceiver or hubtransceiver 106, as described above.

The hub transceiver assigns, to each of the edge transceivers, arespective subset of the optical subcarriers for use in communicatingover the optical communications network (block 3154). Each of thesubsets of the optical subcarriers includes a respective data opticalsubcarrier for transmitting data over the optical communicationsnetwork. Further, at least one of the subsets of the optical subcarriersincludes one or more respective idle optical subcarriers. In someimplementations, the subsets of the optical subcarriers do not overlap.

In some implementations, for at least one of the subsets of the opticalsubcarriers, the data optical subcarrier and the one or more idleoptical subcarriers can be continuous (e.g., spectrally continuous, suchthat there are no optical other optical subcarriers positioned betweenthem spectrally).

In some implementations, for at least at least one of the subsets of theoptical subcarriers, the data optical subcarrier can precede the one ormore idle optical subcarriers (e.g., spectrally precede the one or moreidle optical subcarriers).

Additional details regarding data and idle optical subcarriers aredescribed, for example, with respect to FIG. 24 .

The hub transceiver transmits, to each of the edge transceivers, anindication of the respective subset of the optical subcarriers assignedto the edge transceiver (block 3156). In response, the edge transceivercan transmit and/or receive data over the optical communication networkusing the subset of the optical subcarriers that were assigned to it.

In some implementations, the hub transceiver can include an externalconnection interface for coupling to a network node. For example, thehub transceiver can include one or more of the physical communicationinterfaces shown and described with respect to FIG. 30 . In someimplementations, the network node can be a primary node or hub node 106

Additional details regarding the process 3150 are described, forexample, with respect to FIG. 24 .

FIG. 31F shows an example process 3160 that can be performed using oneor more of the systems described herein. For instance, the process 3160can be performed using an optical communication system including aprimary transceiver and a plurality to secondary transceivers (e.g., asshown in FIGS. 1, 2A-2C, and 18 ).

According to the process 3160, a hub transceiver determines a pluralityof optical subcarriers available for assignment by the hub transceiverto a plurality of edge transceivers for use in communicating over anoptical communications network (block 3162). The hub transceiver iscommunicatively coupled to a first network node and to the opticalcommunications network.

Each of the edge transceivers is configured to be communicativelycoupled to a respective second network node and to the opticalcommunications network. Further, each of the edge transceivers has oneof several types of configurations. For example, one or more of the edgetransceiver can have a first type of configuration for communicatingwith the optical communications network according to a first bandwidth,where the first type of configuration is associated with a first opticalsubcarrier assignment protocol. As another example, one or more of theedge transceiver can have a second type of configuration forcommunicating with the optical communications network according to asecond bandwidth, where the second type of configuration is associatedwith a second optical subcarrier assignment protocol. As anotherexample, one or more of the edge transceiver can have a third type ofconfiguration for communication with the optical communications networkaccording to a third bandwidth, where the third type of configuration isassociated with a third optical subcarrier assignment protocol.

In some implementations, the first bandwidth can be greater than thesecond bandwidth, and the second bandwidth can be greater than the thirdbandwidth. As an example, the first bandwidth can be 100 Gbit/s, thesecond bandwidth can be 50 Gbit/s, and the third bandwidth can be 25Gbit/s.

Although three types of configurations are described above, fewer typesof configurations or a greater number of types of configurations arealso possible, depending on the implementation.

The hub transceiver assigns, to each of the edge transceivers, arespective subset of the optical subcarriers for use in communicatingover the optical communications network (block 3164). In someimplementations, the subsets of the optical subcarriers do not overlap.

Assigning the respective subset of the optical subcarriers can include,for each particular one of the edge transceivers, determining that theparticular edge transceiver has the first type of configuration, thesecond type of configuration, or the third type of configuration. Inresponse, the hub transceiver can assign the respective subset of theoptical subcarriers to the particular edge transceiver according to aparticular one of the optical subcarrier assignment protocols associatedwith the determined type of configuration.

In some implementations, the plurality of optical subcarriers can aplurality of groups, where each of the groups includes N contiguousoptical subcarriers. In some implementations, N can be 4, or some othernumber (e.g., 8, 16, etc.).

In some implementations, assigning the respective subset of the opticalsubcarriers to the particular edge transceiver according to the firstoptical subcarrier assignment protocol can include determining that theoptical subcarriers of a first group among the plurality of groups arenot currently assigned to any of the edge transceivers, and in response,assigning at least one of the optical subcarriers of the first group tothe particular edge transceiver.

Additional details regarding the first optical subcarrier assignmentprotocol are described, for example, with respect to FIG. 24 (e.g., theprotocol described with respect the 100 Gbit/s transceivers).

In some implementations, assigning the respective subset of the opticalsubcarriers to the particular edge transceiver according to the secondoptical subcarrier assignment protocol can include determining that atleast two but less than N of the optical subcarriers of a first groupamong the plurality of groups are not currently assigned to any of theedge transceivers, and in response, assigning at least one of theoptical subcarriers of the first group to the particular edgetransceiver.

Further, in some implementations, assigning the respective subset of theoptical subcarriers to the particular edge transceiver according to thesecond optical subcarrier assignment protocol can include determiningthat none of the groups has at least two but less than N opticalsubcarriers that are not currently assigned to any of the edgetransceivers. In response, the hub transceiver can determine that theoptical subcarriers of a first group among the plurality of groups arenot currently assigned to any of the edge transceivers, and assign atleast one of the optical subcarriers of the first group to theparticular edge transceiver.

Additional details regarding the second optical subcarrier assignmentprotocol are described, for example, with respect to FIG. 24 (e.g., theprotocol described with respect the 50 Gbit/s transceivers).

In some implementations, assigning the respective subset of the opticalsubcarriers to the particular edge transceiver according to the thirdoptical subcarrier assignment protocol can include determining thatexactly one of the optical subcarriers of a first group among theplurality of groups are not currently assigned to any of the edgetransceivers, and in response, assigning one of the optical subcarriersof the third group to the particular edge transceiver.

Further, in some implementations, assigning the respective subset of theoptical subcarriers to the particular edge transceiver according to thethird optical subcarrier assignment protocol can include determiningthat none of the groups has exactly one optical subcarrier that is notcurrently assigned to any of the edge transceivers. In response, the hubtransceiver can determine that a first optical subcarrier of a firstgroup among the plurality of groups is not currently assigned to any ofthe edge transceivers, and that a second optical subcarrier of the firstgroup is currently assigned to one of the edge transceivers, where thefirst optical subcarrier and the second optical subcarrier arecontiguous. Further, in response, the hub transceiver can assign one ofthe optical subcarriers of the first group to the particular edgetransceiver.

Further, in some implementations, assigning the respective subset of theoptical subcarriers to the edge transceiver according to the thirdoptical subcarrier assignment protocol can including determining thatnone of the groups has exactly one optical subcarrier that is notcurrently assigned to any of the edge transceivers, and that none of thegroups has (i) a first optical subcarrier that is not currently assignedto any of the edge transceivers, and (ii) a second optical subcarrierthat is currently assigned, where the first optical subcarrier and thesecond optical subcarrier are contiguous. In response, the hubtransceiver can determine that the optical subcarriers of a first groupamong the plurality of groups are not currently assigned to any of theedge transceivers, and assign at least one of the optical subcarriers ofthe first group to the edge transceiver.

Additional details regarding the third optical subcarrier assignmentprotocol are described, for example, with respect to FIG. 24 (e.g., theprotocol described with respect the 25 Gbit/s transceivers).

The hub transceiver transmits, to each respective one of the edgetransceivers, an indication of the respective subset of the opticalsubcarriers assigned to the particular edge transceiver (block 3166).

IX. Example Computer Systems

Some implementations of subject matter and operations described in thisspecification can be implemented in digital electronic circuitry, or incomputer software, firmware, or hardware, including the structuresdisclosed in this specification and their structural equivalents, or incombinations of one or more of them. For example, in someimplementations, some or all of the components described herein can beimplemented using digital electronic circuitry, or in computer software,firmware, or hardware, or in combinations of one or more of them. Inanother example, the process ### can be implemented using digitalelectronic circuitry, or in computer software, firmware, or hardware, orin combinations of one or more of them.

Some implementations described in this specification can be implementedas one or more groups or modules of digital electronic circuitry,computer software, firmware, or hardware, or in combinations of one ormore of them. Although different modules can be used, each module neednot be distinct, and multiple modules can be implemented on the samedigital electronic circuitry, computer software, firmware, or hardware,or combination thereof.

Some implementations described in this specification can be implementedas one or more computer programs, i.e., one or more modules of computerprogram instructions, encoded on computer storage medium for executionby, or to control the operation of, data processing apparatus. Acomputer storage medium can be, or can be included in, acomputer-readable storage device, a computer-readable storage substrate,a random or serial access memory array or device, or a combination ofone or more of them. Moreover, while a computer storage medium is not apropagated signal, a computer storage medium can be a source ordestination of computer program instructions encoded in an artificiallygenerated propagated signal. The computer storage medium also can be, orcan be included in, one or more separate physical components or media(e.g., multiple CDs, disks, or other storage devices).

The term “data processing apparatus” encompasses all kinds of apparatus,devices, and machines for processing data, including by way of example aprogrammable processor, a computer, a system on a chip, or multipleones, or combinations, of the foregoing. The apparatus can includespecial purpose logic circuitry, e.g., an FPGA (field programmable gatearray) or an ASIC (application specific integrated circuit). Theapparatus also can include, in addition to hardware, code that createsan execution environment for the computer program in question, e.g.,code that constitutes processor firmware, a protocol stack, a databasemanagement system, an operating system, a cross-platform runtimeenvironment, a virtual machine, or a combination of one or more of them.The apparatus and execution environment can realize various differentcomputing model infrastructures, such as web services, distributedcomputing and grid computing infrastructures.

A computer program (also known as a program, software, softwareapplication, script, or code) can be written in any form of programminglanguage, including compiled or interpreted languages, declarative orprocedural languages. A computer program may, but need not, correspondto a file in a file system. A program can be stored in a portion of afile that holds other programs or data (e.g., one or more scripts storedin a markup language document), in a single file dedicated to theprogram in question, or in multiple coordinated files (e.g., files thatstore one or more modules, sub programs, or portions of code). Acomputer program can be deployed to be executed on one computer or onmultiple computers that are located at one site or distributed acrossmultiple sites and interconnected by a communication network.

Some of the processes and logic flows described in this specificationcan be performed by one or more programmable processors executing one ormore computer programs to perform actions by operating on input data andgenerating output. The processes and logic flows also can be performedby, and apparatus also can be implemented as, special purpose logiccircuitry, e.g., an FPGA (field programmable gate array) or an ASIC(application specific integrated circuit).

Processors suitable for the execution of a computer program include, byway of example, both general and special purpose microprocessors, andprocessors of any kind of digital computer. Generally, a processor willreceive instructions and data from a read only memory or a random accessmemory or both. A computer includes a processor for performing actionsin accordance with instructions and one or more memory devices forstoring instructions and data. A computer may also include, or beoperatively coupled to receive data from or transfer data to, or both,one or more mass storage devices for storing data, e.g., magnetic,magneto optical disks, or optical disks. However, a computer need nothave such devices. Devices suitable for storing computer programinstructions and data include all forms of non-volatile memory, mediaand memory devices, including by way of example semiconductor memorydevices (e.g., EPROM, EEPROM, flash memory devices, and others),magnetic disks (e.g., internal hard disks, removable disks, and others),magneto optical disks, and CD-ROM and DVD-ROM disks. The processor andthe memory can be supplemented by, or incorporated in, special purposelogic circuitry.

A computer system may include a single computing device, or multiplecomputers that operate in proximity or generally remote from each otherand typically interact through a communication network. Examples ofcommunication networks include a local area network (“LAN”) and a widearea network (“WAN”), an inter-network (e.g., the Internet), a networkcomprising a satellite link, and peer-to-peer networks (e.g., ad hocpeer-to-peer networks). A relationship of client and server may arise byvirtue of computer programs running on the respective computers andhaving a client-server relationship to each other.

FIG. 32 shows an example computer system 3200 that includes a processor3210, a memory 3220, a storage device 3230 and an input/output device3240. Each of the components 3210, 3220, 3230 and 3240 can beinterconnected, for example, by a system bus 3250. The processor 3210 iscapable of processing instructions for execution within the system 3200.In some implementations, the processor 3010 is a single-threadedprocessor, a multi-threaded processor, or another type of processor. Theprocessor 3010 is capable of processing instructions stored in thememory 3220 or on the storage device 3230. The memory 3220 and thestorage device 3230 can store information within the system 3200.

The input/output device 3240 provides input/output operations for thesystem 3200. In some implementations, the input/output device 3240 caninclude one or more of a network interface device, e.g., an Ethernetcard, a serial communication device, e.g., an RS-232 port, and/or awireless interface device, e.g., an 802.11 card, a 3G wireless modem, a4G wireless modem, a 5G wireless modem, etc. for communicating with anetwork 3070 (e.g., via one or more network devices, such as switches,routers, and/or other network devices). In some implementations, theinput/output device can include driver devices configured to receiveinput data and send output data to other input/output devices, e.g.,keyboard, printer and display devices 3260. In some implementations,mobile computing devices, mobile communication devices, and otherdevices can be used.

While this specification contains many details, these should not beconstrued as limitations on the scope of what may be claimed, but ratheras descriptions of features specific to particular examples. Certainfeatures that are described in this specification in the context ofseparate implementations also can be combined in the sameimplementation. Conversely, various features that are described in thecontext of a single implementation also can be implemented in multipleembodiments separately or in any suitable sub-combination.

A number of implementations have been described. Nevertheless, it willbe understood that various modifications may be made without departingfrom the spirit and scope of the invention. Accordingly, otherimplementations are within the scope of the claims.

What is claimed is:
 1. An apparatus comprising: an optical gatewayconfigured to be communicatively coupled to a plurality of hubtransceivers, wherein the optical gateway is operable to: determine thata first hub transceiver of the plurality of hub transceivers istransmitting first data to the optical gateway by amplitude modulating afirst plurality of optical subcarriers at a first frequency within afirst frequency range, determine that a second hub transceiver of theplurality of hub transceivers is transmitting second data to the opticalgateway by amplitude modulating a second plurality of opticalsubcarriers at a second frequency within a second range, determine thatthe first frequency range overlaps the second frequency range,responsive to determining that the first frequency range overlaps thesecond frequency range, transmit a command to the second hub transceiverto transmit third data to the optical gateway by amplitude modulatingthe second plurality of optical subcarriers at a third frequency withina third frequency range that does not overlap the first frequency range.2. An apparatus in accordance with claim 1, wherein each of the firstplurality of optical subcarriers and each of the second plurality ofoptical subcarriers is a Nyquist subcarrier.
 3. An apparatus inaccordance with claim 1, wherein the optical gateway includes: anoptical tap operable to provide a portion of the first and secondpluralities of optical subcarriers.
 4. An apparatus in accordance withclaim 1, wherein the optical gateway further includes: a photodiodeoptically coupled to the optical tap, the photodiode providing anelectrical signal based on the portion of the first and secondpluralities of optical subcarriers.
 5. An apparatus in accordance withclaim 4, wherein the optical gateway further includes: analog-to-digitalconversion circuitry operable to provide a digital signal associatedwith the electrical signal output from the photodiode.
 6. An apparatusin accordance with claim 5, wherein the optical gateway further includesa microprocessor, the analog-to-digital conversion circuitry beingprovided in the microprocessor.
 7. An apparatus in accordance with claim5, wherein the optical gateway further includes a microcontroller, theanalog-to-digital conversion circuitry being provided in themicrocontroller.
 8. An apparatus in accordance with 5, further includinga low pass filter operable to receive the digital signal.
 9. Anapparatus in accordance with claim 8, further including clock and datarecovery circuitry operable to receive an output from the low passfilter, the clock and data recovery circuitry being operable to provideto output fourth data.
 10. An apparatus in accordance with claim 1,wherein one of the first, second, and third frequency ranges is from 1MHz to 2 MHz.
 11. An apparatus in accordance with claim 1, wherein oneof the first, second, and third frequency ranges is from An apparatus inaccordance with claim 1, wherein one of the first, second, and thirdfrequency ranges is from 3 MHz to 4 MHz.
 12. An apparatus in accordancewith claim 1, wherein one of the first, second, and third frequencyranges is from 6 MHz to 7 MHz.